Deck 4: Applying Newtons Laws

Question 1

A boulder rolls off of a very high cliff.If you disregard air,while it is falling,its trajectory is never truly vertical.

Answer 1

True

Question 2

For general projectile motion if we neglect air,the horizontal component of a projectile's acceleration

A)is always zero.
B)remains a non-zero constant.
C)continuously increases.
D)continuously decreases.
E)first decreases and then increases.

Answer 2

A

Question 3

The eastward component of vector is equal to the westward component of vector and their northward components are equal.Which one of the following statements must be correct for these two vectors?

A)Vector is parallel to vector
B)Vector is antiparallel (in the opposite direction)to vector
C)Vector must be perpendicular to vector
D)The magnitude of vector must be equal to the magnitude of vector
E)The angle between vector and vector must be 90°.

Answer 3

D

Question 4

If a vector pointing upward has a positive magnitude,a vector pointing downward has a negative magnitude.

Question 5

For general projectile motion if we neglect air,the vertical component of a projectile's acceleration

A)is always zero.
B)remains a non-zero constant.
C)continuously increases.
D)continuously decreases.
E)first decreases and then increases.

Question 6

The magnitude of a vector an only zero if all of its components are zero.

Question 7

Vector is along the +x-axis and vector is along the +y-axis.Which one of the following statements is correct with respect to these vectors?

A)The x component of vector is equal to the x component of vector
B)The y component of vector is equal to the y component of vector
C)The x component of vector is equal to the y component of vector
D)The y component of vector is equal to the x component of vector

Question 8

If a vector has components A_x > 0,and A_y < 0,then the angle that this vector makes with the positive x-axis must be in the range

A)0° to 90°
B)90° to 180°
C)180° to 270°
D)270° to 360°
E)cannot be determined without additional information

Question 9

If a vector has components A_x < 0,and A_y < 0,then the angle that this vector makes with the positive x-axis must be in the range

A)0° to 90°
B)90° to 180°
C)180° to 270°
D)270° to 360°
E)cannot be determined without additional information

Question 10

Which of the following statements are true about an object in two-dimensional projectile motion if we neglect air? (There could be more than one correct choice.)

A)The speed of the object is constant but its velocity is not constant.
B)The acceleration of the object is +g when the object is rising and -g when it is falling.
C)The acceleration of the object is zero at its highest point.
D)The speed of the object is zero at its highest point.
E)The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

Question 11

Shown below are the velocity and acceleration vectors for an object in several different types of motion.In which case is the object slowing down and turning to its right?

Question 12

If a vector's components are all negative,then the magnitude of the vector is negative.

Question 13

In an air-free chamber,a pebble is thrown horizontally,and at the same instant a second pebble is dropped from the same height.Compare the times of fall of the two pebbles.

A)The thrown pebble hits first.
B)The dropped pebble hits first.
C)They hit at the same time.
D)We cannot tell without knowing which pebble is heavier.

Question 14

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically.Which object is traveling faster when it hits the level ground below if we neglect air?

A)It is impossible to tell because we do not know their masses.
B)the stone
C)the ball
D)Both are traveling at the same speed.

Question 15

James and John dive from an overhang into the lake below.James simply drops straight down from the edge.John takes a running start and jumps with an initial horizontal velocity of 25 m/s.Compare the time it takes each to reach the lake below if we neglect the effects of air.

A)James reaches the surface of the lake first.
B)John reaches the surface of the lake first.
C)James and John will reach the surface of the lake at the same time.
D)Cannot be determined without knowing the mass of both James and John.
E)Cannot be determined without knowing the weight of both James and John.

Question 16

The magnitude of a vector can never be less than the magnitude of any of its components.

Question 17

A pilot drops a package from a plane flying horizontally at a constant speed.Neglecting effects of air,when the package hits the ground the horizontal location of the plane will

A)be behind the package.
B)be directly over the package.
C)be in front of the package.
D)depend on the speed of the plane when the package was released.

Question 18

James and John dive from an overhang into the lake below.James simply drops straight down from the edge.John takes a running start and jumps with an initial horizontal velocity of 25 m/s.Assuming no effects of air,when they reach the lake below

A)the splashdown speed of James is larger than that of John.
B)the splashdown speed of John is larger than that of James.
C)they will both have the same splashdown speed.
D)the splashdown speed of James must be 9.8 m/s larger than that of John.
E)the splashdown speed of John must be 25 m/s larger than that of James.

Question 19

If a vector has components A_x < 0,and A_y > 0,then the angle that this vector makes with the positive x-axis must be in the range

A)0° to 90°
B)90° to 180°
C)180° to 270°
D)270° to 360°
E)It cannot be determined without additional information.

Question 20

For general projectile motion if we neglect air,the horizontal component of a projectile's velocity

A)remains zero.
B)remains a non-zero constant.
C)continuously increases.
D)continuously decreases.
E)first decreases and then increases.

Question 21

In the figure,what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

A)exactly 2.0 N.
B)exactly 1.0 N
C)0.50 N
D)0.00 N
E)more than 19.6 N

Question 22

The x component of vector is 8.7 units,and its y component is -6.5 units.The magnitude of is closest to

A)9.9 units
B)7.9 units
C)8.9 units
D)11 units
E)12 units

Question 23

A velocity vector has components 36 m/s westward and 22 m/s northward.What are the magnitude and direction of this vector?

Question 24

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal.What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?

A)200 N
B)120 N
C)160 N
D)150 N
E)0 N

Question 25

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same. Which of the figures below shows a correct force diagram of the horizontal forces exerted on the upper block,A?

A)
B)
C)
D)
E)

Question 26

A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal.It reaches its highest point and starts falling down.Which of the following statements about the rock's motion are true just before it hits the ground? (There could be more than one correct choice.)

A)Its horizontal velocity component is zero.
B)Its velocity is vertical.
C)Its vertical velocity component is the same as it was just as it was launched.
D)Its horizontal velocity component is the same as it was just as it was launched.
E)Its speed is the same as it was just as it was launched.

Question 27

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal.What must be true about the force of static friction f exerted on the block?

A)f > mg
B)f > mg cos θ
C)f > mg sin θ
D)f = mg cos θ
E)f = mg sin θ

Question 28

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal.What is the magnitude of the force that the surface of the hill exerts on the sled?

A)200 N
B)120 N
C)160 N
D)150 N
E)0 N

Question 29

Mary and Debra stand on a snow-covered roof.They both throw snowballs with the same initial speed,but in different directions.Mary throws her snowball downward,at 30° below the horizontal; Debra throws her snowball upward,at 30° above the horizontal.Which of the following statements are true about just before the snowballs reach the ground below? Neglect the effects of air.(There could be more than one correct choice.)

A)Debra's snowball will stay in flight longer than Mary's snowball.
B)Mary's snowball will stay in flight longer than Debra's snowball.
C)Both snowballs will take the same amount of time to hit the ground.
D)Debra's snowball has exactly the same acceleration as Mary's snowball.
E)Mary's snowball has a greater downward acceleration than Debra's snowball.

Question 30

Two boxes,A and B,are connected by a horizontal string S on a horizontal floor.A very light wire pulls horizontally on box B,as shown in the figure,exerting a force of 100 N.The Newton's third law pair force to this pull is

A)the pull that box B exerts on string S.
B)the pull that string S exerts on box B.
C)the pull that string S exerts on box A.
D)the pull that box B exerts on the wire.
E)the force that box A exerts on box B.

Question 31

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same. Which of the figures below shows a correct force diagram of the horizontal forces exerted on the lower block,B?

A)
B)
C)
D)
E)None of these diagrams is correct.

Question 32

A person is pushing on a box,exerting a force of magnitude P,as shown in the figure.Earth exerts force W on the box.The push is directed at an angle θ below the horizontal,and the box remains at rest.The box rests on a horizontal floor that has some friction with the box.The friction force exerted by the floor on the box is equal to

A)P sin θ
B)P cos θ
C)0
D)P cos θ + W
E)P + W

Question 33

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal.What must be true about the force F that the ramp exerts on the block perpendicular to the surface of the ramp?

A)F > mg
B)F > mg cos θ
C)F > mg sin θ
D)F = mg cos θ
E)F = mg sin θ

Question 34

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord.The mass of P is greater than that of Q.A horizontal force is exerted on box Q as shown in the figure,accelerating the bodies to the right.The magnitude of the force exerted by the connecting cord on body P is

A)zero.
B)less than F but not zero.
C)equal to F.
D)greater than F.

Question 35

Mary and Debra stand on a snow-covered roof.They both throw snowballs with the same initial speed,but in different directions.Mary throws her snowball downward,at 30° below the horizontal; Debra throws her snowball upward,at 30° above the horizontal.Which of the following statements are true about just as the snowballs reach the ground below? Neglect the effects of air.(There could be more than one correct choice.)

A)Debra's snowball will have a higher speed than Mary's snowball.
B)Mary's snowball will have a higher speed than Debra's snowball.
C)Both snowballs will hit the ground with the same speed.
D)Both snowballs hit the ground at the same time.
E)Mary's snowball reaches the ground before Debra's snowball.

Question 36

Two objects of unequal masses,M and m (M > m),are connected by a very light cord passing over an ideal pulley of negligible mass.When released,the system accelerates,and friction is negligible. Which one of the following force diagrams most realistically represents the forces exerted on the two objects in the moving system?

A)
B)
C)
D)

Question 37

A player kicks a soccer ball in a high arc toward the opponent's goal.At the highest point in its trajectory

A)both the velocity and the acceleration of the soccer ball are zero.
B)neither the ball's velocity nor its acceleration are zero.
C)the ball's acceleration is zero but its velocity is not zero.
D)the ball's acceleration points upward.
E)the ball's velocity points downward.

Question 38

A person is pushing on a box exerting a force of magnitude P, as shown in the figure.Earth exerts a force W on the box.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The force that the surface exerts on the box perpendicular to the surface is equal to

A)W.
B)W + P.
C)W + P cos θ.
D)W + P sin θ.
E)W - P sin θ.

Question 39

Two boxes are connected to each other by a string as shown in the figure.The 10-N box slides without friction on the horizontal table surface.The pulley is ideal and the string has negligible mass.What is true about the tension force T that the string exerts on the boxes?

A)T = 10 N
B)T = 20 N
C)T = 30 N
D)T < 30 N
E)T > 30 N

Question 40

Two objects have masses m and 5m,respectively.They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance.Which one of the following statements about these objects is correct?

A)It takes the lighter object 5 times longer to reach the bottom of the ramp than the heavier.
B)It takes the lighter object 10 times longer to reach the bottom of the ramp than the heavier.
C)It takes the heavier object 5 times longer to reach the bottom of the ramp than the lighter.
D)It takes the heavier object 10 times longer to reach the bottom of the ramp than the lighter.
E)The two objects reach the bottom of the ramp at exactly the same time.

Question 41

The x component of vector is 5.3 units,and its y component is -2.3 units.The angle that vector makes with the +x-axis is closest to

A)340°
B)160°
C)250°
D)110°
E)23°

Question 42

A vector has components A_x = 12.0 m and A_y = 5.00 m.
(a)What is the angle that vector makes with the +x-axis?
(b)What is the magnitude of vector ?

Question 43

A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff.A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s.What is the height of the cliff if effects of air are negligible?

A)22 m
B)43 m
C)77 m
D)91 m

Question 44

A boy throws a rock with an initial velocity of at 30.0° above the horizontal.How long does it take for the rock to reach the maximum height of its trajectory if effects of air are negligibly small and g = 9.80 m/s²?

A)0.160 s
B)0.282 s
C)0.313 s
D)0.441 s

Question 45

The x and y components of a vector in a horizontal plane are 4.00 m and 3.00 m,respectively.
(a)What is the magnitude of this vector?
(b)What angle does this vector make with the positive +y-axis.

Question 46

A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal.If we can neglect air,what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

A)10 m/s
B)17 m/s
C)20 m/s
D)zero

Question 47

A player throws a football 50.0 m at 61.0° north of west.What is the westward component of the displacement of the football?

A)64.7m
B)55.0 m
C)0.00 m
D)74.0 m
E)24.2 m

Question 48

The free-fall acceleration on the Moon is only one-sixth of that on Earth,and the Moon has no atmosphere.If you hit a baseball on the Moon with the same effort (and therefore at the speed and angle)as on Earth,how far would the ball would travel on the Moon compared to on Earth? Neglect effects of air on Earth.

A)1/6 as far as on Earth
B)36 times as far as on Earth
C)the same distance as on Earth
D)6 times as far as on Earth
E) as far as on Earth

Question 49

A vector in the xy-plane has an x component of -7.50 units.What must be the y component of this vector so that its magnitude is 10.0 units.(Note: There are two possible answers.)

Question 50

A girl throws a rock horizontally,with a velocity of 10 m/s,from a bridge.It falls 20 m to the water below.How far does the rock travel horizontally before striking the water,assuming negligible air effects?

A)14 m
B)16 m
C)20 m
D)24 m

Question 51

The magnitude of is 5.5 m,and this vector lies in the second quadrant and makes an angle of 34 ° with the +y-axis.The components of are closest to:

A) = -3.1 m, = 4.6 m.
B) = 3.1 m, = -4.6 m.
C) = 4.6 m, = -3.1 m.
D) = -4.6 m, = 3.1 m.
E) = -4.6 m, = -3.1 m.

Question 52

A ball thrown horizontally from a point 24 m above the ground,strikes the ground after traveling horizontally a distance of 18 m.With what speed was it thrown,assuming negligible air effects?

A)6.1 m/s
B)7.4 m/s
C)8.1 m/s
D)8.9 m/s

Question 53

A boy jumps with a velocity of magnitude 20.0 m/s at an angle of 25.0° above the horizontal.What is the horizontal component of the boy's velocity?

A)18.1 m/s
B)15.6 m/s
C)8.45 m/s
D)12.6 m/s
E)9.33 m/s

Question 54

The components of vectors and are given as follows: = -9.2 = -4.5 = -6.1 = 4.3 The angle (less than 180°)between vectors and is closest to

A)77°.
B)103°.
C)10°.
D)170°.
E)84°.

Question 55

As shown in the figure,a heavy rock is shot upward from the edge of a vertical cliff.It leaves the edge of the cliff with an initial velocity of 15 m/s directed at 25° from the vertical.Assume that air has no effect on the motion of the rock.How high is the cliff?

Question 56

A displacement vector is 34.0 m in length and is directed 60.0° east of north.Selecting from the choices in the table below,what are the components of this vector? Northward Eastward
Choice component component
1 29.4 m 17.0 m
2 18.2 m 28.1 m
3 22.4 m 11.5 m
4 17.0 m 29.4 m
5 25.2 m 18.2 m

A)choice 1
B)choice 2
C)choice 3
D)choice 4
E)choice 5

Question 57

When rolled down a mountainside at 7.0 m/s,the horizontal component of its velocity vector was 1.8 m/s.What was the angle of the mountain surface above the horizontal?

A)75°
B)57 °
C)33°
D)15°

Question 58

A ball is thrown at an original speed of 8.0 m/s at an angle of 35° above the horizontal.If there is no air,what is the speed of the ball when it returns to the same horizontal level?

A)4.0 m/s
B)8.0 m/s
C)16 m/s
D)9.8 m/s

Question 59

A player hits a tennis ball into the air with an initial velocity of 32 m/s at 35° from the vertical.How fast is the ball moving at the highest point in its trajectory if effects of air are negligible?

Question 60

When Jeff ran up a hill at 7.0 m/s,the horizontal component of his velocity vector was 5.1 m/s.What was the vertical component of Jeff's velocity?

A)4.8 m/s
B)4.3 m/s
C)3.8 m/s
D)3.4 m/s

Question 61

In a room where g = 9.81 m/s²,a hockey puck slides off the edge of a platform with an initial velocity of 28.0 m/s horizontally.The height of the platform above the ground is 2.00 m.What is the speed of the puck just before it hits the ground? Ignore air.

A)48.2 m/s
B)28.7 m/s
C)28.0 m/s
D)26.3 m/s
E)6.26 m/s

Question 62

A cat leaps to try to catch a bird.If the cat's jump was at 60° off the ground and its initial velocity was what is the highest point of its trajectory,neglecting effects of air?

A)0.29 m
B)0.58 m
C)10.96 m
D)0.19 m

Question 63

At target practice,a rifle bullet is fired at an angle of 30° below the horizontal with an initial velocity of 800 m/s from the top of a cliff 80 m high.How far from the base of the cliff does it strike the level ground below if air effects are negligible?

Question 64

A batter hits a home run in which the ball travels 110 m horizontally with no appreciable effects of air.If the ball left the bat at 50° above the horizontal just above ground level,how fast was it hit?

Question 65

You throw a rock horizontally off a cliff with a speed of 20 m/s.Assuming no effects of air,after 2.0 s,the magnitude of the velocity of the rock is closest to

A)28 m/s
B)20 m/s
C)40 m/s
D)37 m/s

Question 66

A shell is launched with a velocity of 100 m/s at an angle of 30.0° above horizontal from a point on a cliff 50.0 m above a level plain below.How far from the base of the cliff does the shell strike the ground? There are no appreciable effects of air,and g = 9.80 m/s² at the location of the cliff.

Question 67

A marble moving 1.48 m/s rolls off the top edge of a 125-cm high table in a room where there is no appreciable air resistance and the free-fall acceleration is 9.80 m/s².Neglect effects of air.
(a)How far from the base of the table will it strike the floor?
(b)How long will it be in the air?

Question 68

A football kicker is attempting a field goal from out.The ball is kicked and just clears the lower bar with a time of flight of If the angle of the kick was 45°,what was the initial speed of the ball,assuming no effects of air?

A)21.5 m/s
B)19.7 m/s
C)2.2 m/s
D)39 m/s

Question 69

A hockey puck slides off the edge of a horizontal platform with an initial velocity of 20 m/s horizontally.The effects of air are negligible.The height of the platform above the ground is 2.0 m.What is the magnitude of the vertical component of the velocity of the puck just before it hits the ground?

A)20 m/s
B)6.3 m/s
C)13 m/s
D)15 m/s
E)21 m/s

Question 70

A hockey puck slides off the edge of a platform with an initial velocity of 20 m/s horizontally.The height of the platform above the ground is 2.0 m.What is the magnitude of the velocity of the puck just before it touches the ground? You can neglect air.

A)21 m/s
B)22 m/s
C)24 m/s
D)25 m/s
E)6.3 m/s

Question 71

A fisherman casts his bait toward the river at an angle of 25° above the horizontal.As the line unravels,he notices that the bait and hook reach a maximum height of What was the initial velocity he launched the bait with? Assume that the line exerts no appreciable drag force on the bait and hook and that is the effects of air are negligible.

A)18 m/s
B)7.9 m/s
C)7.6 m/s
D)6.3 m/s

Question 72

A ball rolls over the edge of a platform with a horizontal velocity of magnitude v.The height of the platform is 1.6 m and the horizontal range of the ball from the base of the platform is 20 m.What is the magnitude of v if you can ignore air?

Question 73

A celebrating student throws a water balloon horizontally from a dormitory window that is 50 m above the ground.It hits the ground at a point 60 m from the building.Ignore air.
(a)What will be the horizontal component of the velocity of the balloon just before it hits the ground?
(b)What will be the magnitude of the vertical velocity of the balloon just before it hits the ground?

Question 74

A hockey puck slides off the edge of a horizontal platform with an initial velocity of 28.0 m/shorizontally in a city where the free-fall acceleration is 9.81 m/s².The height of the platform above the ground is 2.00 m.What is the angle below the horizontal of the velocity of the puck just before it hits the ground if you ignore the effects of air?

A)77.2°
B)72.6°
C)12.8°
D)12.6°
E)31.8°

Question 75

A girl throws a rock horizontally with a speed of 12 m/s from a bridge.It falls 2.28 s before hitting the water below.Neglect air.
(a)How high is the bridge from the water below?
(b)How far horizontally does the rock travel before striking the water?

Question 76

Enzo throws a rock horizontally with a speed of 12 m/s from a bridge.It falls for 2.28 s before reaching the water below.Ignore air.Just as the rock reaches the water,find
(a)the horizontal component of its velocity.
(b)the speed with which it is moving.

Question 77

A hunter points a rifle horizontally and holds it 3.30 m above the ground.The bullet leaves the barrel at 325 m/s.Ignore air and assume that free-fall acceleration is 9.80 m/s².
(a)How long does it take for the bullet to strike the ground?
(b)How far horizontally does it travel?

Question 78

A plane flying horizontally at a speed of 50 m/s and at an elevation of 160 m drops a package,and 2.0 s later it drops a second package.How far apart will the two packages land on the ground if effects of air resistance are negligible?

A)100 m
B)160 m
C)180 m
D)320 m

Question 79

A ball rolls over the edge of a platform with only a horizontal velocity.The height of the platform is 1.6 m and the horizontal range of the ball from the base of the platform is 20 m.What is the horizontal velocity of the ball just before it touches the ground? Neglect air.

A)35 m/s
B)9.8 m/s
C)20 m/s
D)4.9 m/s
E)70 m/s

Question 80

A projectile is shot horizontally at 23.4 m/s from the roof of a building 55 m tall.
Effects of air are negligible.
(a)Determine the time necessary for the projectile to reach the ground below.
(b)Determine the distance from the base of the building that the projectile lands.
(c)Determine the horizontal and vertical components of the velocity just before the projectile reaches the ground.