Deck 2: Motion, Forces, and Newtons Laws

Question 1

Which of the following is not a vector quantity?

A) temperature
B) velocity
C) acceleration
D) displacement

Answer 1

temperature

Question 2

In one-dimensional motion where the direction is indicated by a plus or minus sign, the average velocity of an object has which of the following properties?

A) It is positive.
B) It is negative.
C) It is zero.
D) It can be positive, negative, or zero.

Answer 2

It can be positive, negative, or zero.

Question 3

Changing the positive direction in a reference frame to the opposite direction does not change the sign of which of the following quantities?

A) velocity
B) average velocity
C) speed
D) displacement

Answer 3

speed

Question 4

Jeff throws a ball straight up. For which situation is the vertical velocity zero?

A) on the way up
B) at the top
C) on the way back down
D) none of the above

Question 5

When we add a displacement vector to another displacement vector, the result is:

A) a velocity.
B) an acceleration.
C) another displacement.
D) a scalar.

Question 6

A truck moves 70 m west, then moves 120 m east, and finally moves west again a distance of 90 m. If east is chosen as the positive direction, what is the truck's resultant displacement?

A) "40 m"
B) "- 40 m"
C) "280 m"
D) "-280 m"

Question 7

In one-dimensional motion, the average speed of an object that moves from one place to another and then back to its original place has which of the following properties?

A) It is positive.
B) It is negative.
C) It is zero.
D) It can be positive, negative, or zero.

Question 8

Displacement is which of the following types of quantities?

A) vector
B) scalar
C) magnitude
D) dimensional

Question 9

A change in a physical quantity w having initial value w_i and final value w_f is given by which of the following?

A) w_i- w_f
B) w_f - w_i
C) (w_f + w_i)/2
D) none of the above

Question 10

A railroad train travels forward along a straight track at 80.0 m/s for 1000 m and then travels at 40.0 m/s for the next 1000 m. What is the average velocity?

A) 60.0 m/s
B) 37.5 m/s
C) 63.7 m/s
D) 53.3 m/s

Question 11

Which formula is dimensionally consistent with an expression yielding a value for velocity? (a is acceleration, x is distance, and t is time)

A) v/t²
B) vx²
C) v²/t
D) at

Question 12

When NASA was communicating with astronauts on the Moon, the time from sending on the Earth to receiving on the moon was 1.33 s. Find the distance from Earth to the Moon. (The speed of radio waves is 3.00 * 10⁸ m/s.)

A) 240,000 km
B) 384,000 km
C) 399,000 km
D) 768,000 km

Question 13

A ball is thrown vertically upwards at 9.8 m/s. For its complete trip (up and back down to the starting position), its average velocity is:

A) 19.6 m/s.
B) 9.80 m/s.
C) 4.90 m/s.
D) not given.

Question 14

An object moves 10 m east in 30 s and then returns to its starting point taking an additional 70 s. If west is chosen as the positive direction, what is the average speed of the object?

A) 0.20 m/s
B) -0.20 m/s
C) 0.50 m/s
D) 0 m/s

Question 15

On a position-time graph, the slope of the straight line joining two points on the plotted curve that are separated in time by the interval $\Delta$ t, is which of the following quantities?

A) average steepness
B) average velocity
C) instantaneous velocity
D) average acceleration

Question 16

A bird, accelerating from rest at a constant rate, experiences a displacement of 37 m in 11 s. What is the average velocity?

A) 1.7 m/s
B) 2.5 m/s
C) 3.4 m/s
D) zero

Question 17

In which of the following cases is the displacement's magnitude half the distance traveled?

A) 10 steps east followed by 3 steps west
B) 22 steps east followed by 11 steps west
C) 5 steps east followed by 10 steps west
D) 15 steps east followed by 5 steps west

Question 18

The distance of the Earth from the Sun is 93,000,000 miles. If there are 3.15 *10⁷ s in one year, find the speed of the Earth in its orbit about the Sun.

A) 9.28 miles/s
B) 18.6 miles/s
C) 27.9 miles/s
D) 37.2 miles/s

Question 19

An object moves 20 m east in 30 s and then returns to its starting point taking an additional 50 s. If west is chosen as the positive direction, what is the sign associated with the average velocity of the object?

A) "+"
B) "-"
C) "0 (no sign)"
D) "any of the above"

Question 20

If a is acceleration, v is velocity, x is position, and t is time, then which equation is not dimensionally correct?

A) t = x/v
B) a = v²/x
C) v = a/t
D) t² = 2x/a

Question 21

A v-t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 6 s the acceleration of the ball is zero. We know that at t = 6 s,

A) the slope of the curve is non-zero.
B) the curve is not crossing the time axis.
C) the velocity of the ball is not changing.
D) the curve is at v = 0, t = 0.

Question 22

An x-t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 6 s the velocity of the ball is zero. We can be positive that at t = 6 s,

A) the slope of the curve is non-zero.
B) the acceleration is constant.
C) the ball has stopped.
D) none of the above answers is always correct.

Question 23

A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100 km/hr in 8.00 s. What is the speed after the first 5.00 s of acceleration? (Hint: First convert the speed to m/s.)

A) 34.7 m/s
B) 44.4 m/s
C) 23.1 m/s
D) 17.4 m/s

Question 24

A bird, accelerating from rest at a constant rate, experiences a displacement of 37 m in 11 s. What is its acceleration?

A) 0.20 m/s²
B) 0.31 m/s²
C) 0.51 m/s²
D) 0.61 m/s²

Question 25

An object, initially moving in the negative x direction, is subjected to a change in velocity in the negative y direction. If the resulting velocity vector is drawn from the origin, into which quadrant does this vector point?

A) 1st
B) 2nd
C) 3rd
D) None, since the object is now moving in the negative y direction.

Question 26

A strobe photograph of a car moving along a straight road shows the interval between each successive image to be diminishing. If the direction of motion of the car is taken as positive, which of the following are negative?

A) the speed of the car
B) the average velocity of the car
C) the average acceleration of the car
D) all of the above

Question 27

A particle moves east at constant velocity for a time interval t. It then moves north at a constant velocity, with the same speed as before, for another time interval t Finally it moves east again with the original velocity. At the instant an additional time interval t has elapsed, which of the following are true about the average velocity and the average acceleration for the motion described?

A) The average velocity is and the average acceleration is zero.
B) The average velocity is and the average acceleration is not zero.
C) The average velocity is not and the average acceleration is zero.
D) The average velocity is not and the average acceleration is not zero.

Question 28

A 50-g ball traveling at 25.0 m/s is bounced off a brick wall and rebounds at 20.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the magnitude of the average acceleration of the ball during this time interval?

A) 714 m/s²
B) 1430 m/s²
C) 6430 m/s²
D) 12,900 m/s²

Question 29

The slope of the acceleration-time curve represents:

A) the velocity.
B) the rate of change of acceleration.
C) the rate of change of displacement.
D) the area under the position vs. time curve.

Question 30

The value of an object's acceleration may be characterized in equivalent words by which of the following?

A) displacement
B) rate of change of displacement
C) velocity
D) rate of change of velocity

Question 31

A ball is pushed downhill with an initial velocity of 3.0 m/s. The ball rolls down a hill with a constant acceleration of 1.6 m/s². The ball reaches the bottom of the hill in 6.0 s. What is the ball's velocity at the bottom of the hill?

A) 10 m/s
B) 13 m/s
C) 16 m/s
D) 17 m/s

Question 32

An object moves at a constant velocity of 12 m/s to the southwest for an interval of 20 s. Halfway through this interval, what is the magnitude of its instantaneous velocity?

A) It can be any value from 0 to 24 m/s.
B) 6 m/s
C) 12 m/s
D) More information is needed.

Question 33

A car is initially moving at 30 m/s east and a little while later it is moving at 10 m/s north. Which of the following best describes the orientation of the average acceleration during this time interval?

A) north of west
B) northwest
C) west
D) north of east

Question 34

A strobe photograph shows equally spaced images of a car moving along a straight road. If the time intervals between images is constant, which of the following cannot be positive?

A) the speed of the car
B) the average velocity of the car
C) the acceleration of the car
D) the direction of motion of the car

Question 35

A bird, accelerating from rest at a constant rate, experiences a displacement of 37 m in 11 s. What is the final velocity after 11 s?

A) 6.7 m/s
B) 5.1 m/s
C) 13 m/s
D) zero

Question 36

A European sports car dealer claims that his car will accelerate at a constant rate from rest to 100 km/hr in 8.00 s. If so, what is the acceleration? (Hint: First convert speed to m/s.)

A) 3.47 m/s²
B) 4.63 m/s²
C) 11.4 m/s²
D) 18.5 m/s²

Question 37

An object is dropped from a height. Once it is moving, which of the following statements is true, at least at one point?

A) Its velocity is more than its acceleration.
B) Its velocity is less than its acceleration.
C) Its velocity is the same as its acceleration.
D) Its velocity is never equal to its acceleration.

Question 38

In the case of constant acceleration, the average velocity equals the instantaneous velocity:

A) at the beginning of the time interval.
B) at the end of the time interval.
C) half-way through the time interval.
D) three-fourths of the way through the time interval.

Question 39

A hiker walks 200 m east and then walks 100 m north. In what direction is her resulting displacement?

A) north
B) east
C) northeast
D) None of the answers is correct.

Question 40

The first displacement is 7 m and the second displacement is 3 m. They cannot add together to give a total displacement of:

A) 10 m.
B) 7 m.
C) 4 m.
D) 3 m.

Question 41

A jogger runs halfway around a circular path with a radius of 70 m. What, respectively, are the magnitude of the displacement and the distance jogged?

A) 70 m, 220 m
B) 70 m, 440 m
C) 140 m, 220 m
D) 140 m, 440 m

Question 42

A car is moving along a straight highway and accelerates at a constant rate while going from point A to point B. If the acceleration is positive, increasing the speed of the car, where does the position where the instantaneous speed equals the average speed occur for the interval from A to B?

A) midway between A and B
B) closer to A than to B
C) closer to B than to A
D) Any of the answers could be correct depending on the original speed.

Question 43

A physics student is riding on a train traveling north. Having read about inertia, the student performs an experiment with a golf ball. He reaches over the aisle and drops the ball from rest. Instead of hitting the floor directly below the student's hand, it hits to the north, i.e., forward of that position. Which of the following might be the cause for this to happen?

A) The train is moving at constant velocity.
B) The train is speeding up.
C) The train is slowing down.
D) Whatever the cause, it cannot be any of the answers given.

Question 44

The statement by Newton that "for every action there is an opposite but equal reaction" is regarded as which of his laws of motion?

A) first
B) second
C) third
D) fourth

Question 45

Two forces act on a 6.00-kg object. One of the forces is 11.0 N. If the object accelerates at 2.00 m/s², what is the greatest possible magnitude of the other force?

A) 33.0 N
B) 23.0 N
C) 3.0 N
D) 1.0 N

Question 46

A runner circles a track of radius 100 m in 100 s moving at a constant rate. If the runner was initially moving east, what has been the runner's average acceleration when halfway around the track?

A) At a constant rate, the average acceleration would be zero.
B) 0.13 m/s², south
C) 0.25 m/s², west
D) No answer is correct.

Question 47

A car is moving in the positive direction along a straight highway and accelerates at a constant rate while going from point A to point B. If the acceleration is positive, increasing the speed of the car, when does the position where the average speed equals the instantaneous speed occur during the time interval from A to B? Assume the time interval is T.

A) T/2 from the start of the interval
B) before T/2 from the start of the interval
C) after T/2 from the start of the interval
D) It depends on the speed at the start of the time interval.

Question 48

On a velocity-time graph for a particle, suppose the plot starts at some positive velocity and then follows a straight line to zero at a later time. Which of the following must be true about a position vs. time graph for this same time interval?

A) The curve will start at a positive position value and follow a straight line to zero at the later time.
B) The curve will rise steeply at first and as time goes on will level out approaching its highest position value at the later time.
C) The curve will drop steeply at first and as time goes on will approach its lowest position value at the later time
D) The curve will start at the zero of position and follow a straight line to its highest position at the later time.

Question 49

Five boys are pushing on a snowball, and each is pushing with a force of 20.0 N. However, each boy is pushing in a different direction. They are pushing north, northeast, east, southeast, and south. (Each boy is pushing at an angle of 45.0 $\degree$ relative to his neighbor.) What is the magnitude of the total force on the ball?

A) 54.2 N
B) 48.3 N
C) 24.1 N
D) 0 N

Question 50

An airplane of mass 1.2 *10⁴ kg tows a glider of mass 0.6 * 10⁴ kg. The airplane propellers provide a net forward thrust of 5.4 * 10⁴ N. What is the glider's acceleration?

A) 2.0 m/s²
B) 3.0 m/s²
C) 6.0 m/s²
D) 9.8 m/s²

Question 51

If we know that a nonzero net force is acting on an object, which of the following must we assume regarding the object's condition? The object is:

A) at rest.
B) moving with a constant velocity.
C) being accelerated.
D) losing mass.

Question 52

A 7.0-kg bowling ball experiences a net force of 6.0 N. What will be its acceleration?

A) 0.86 m/s²
B) 6.0 m/s²
C) 7.0 m/s²
D) 42 m/s²

Question 53

An automobile of mass 2000 kg moving at 20 m/s is braked suddenly with a constant braking force of 10,000 N. How far does the car travel before stopping?

A) 40 m
B) 80 m
C) 120 m
D) 160 m

Question 54

An astronaut applies a force of 500 N to an asteroid, and it accelerates at 3.00 m/s². What is the asteroid's mass?

A) 1500 kg
B) 135 kg
C) 600 kg
D) 167 kg

Question 55

On a position-time graph for a particle, suppose the plot starts at some positive position and as the time goes on the curve gets steeper and steeper while curving upwards. Which of the following must be true?

A) The speed of the particle is constant.
B) The acceleration of the particle is constant.
C) The speed of the particle is decreasing.
D) The acceleration of the particle is positive.

Question 56

Arvin the Ant is on a picnic table. He travels 30 cm eastward, then 20 cm northward, and finally 15 cm westward. What is the magnitude of Arvin's net displacement?

A) 25 cm
B) 65 cm
C) 50 cm
D) 29 cm

Question 57

If we know an object is moving at constant velocity, we may assume:

A) the net force acting on the object is zero.
B) there are no forces acting on the object.
C) the object is accelerating.
D) the object is losing mass.

Question 58

Which of the following expresses a principle which was initially stated by Galileo and was later incorporated into Newton's laws of motion?

A) An object's acceleration is inversely proportional to its mass.
B) For every action there is an equal but opposite reaction.
C) The natural condition for a moving object is to remain in motion.
D) The natural condition for a moving object is to come to rest.

Question 59

Suppose a particle is moving along a straight line with a speed v for a time t, then stops for a time t, and then resumes moving along the original direction with speed v for time t. What has been the average speed of the particle for the total time period 3t?

A) v
B)
C) 1.5 v
D)

Question 60

The net force on an object in the positive x direction. Consider the following statements: i) The object can be moving in the negative x direction.
ii. The object can be speeding up.
iii. The object can be slowing down.
iv. The object can be moving in the positive y direction.
Which of the statements are true?

A) (i) and (ii)
B) (ii) and (iii)
C) (iii) and (iv)
D) Choose this answer if all the statements are true.

Question 61

A thrown stone hits a window but doesn't break it. Instead, it reverses direction and ends up on the ground below the window. In this case, we know:

A) the force of the stone on the glass > the force of the glass on the stone.
B) the force of the stone on the glass = the force of the glass on the stone.
C) the force of the stone on the glass < the force of the glass on the stone.
D) the stone didn't slow down as it hit the glass.