Question 1

Two projectiles, A and B, are launched with equal initial speeds. Projectile A is launched at angle 35° and projectile B at angle 55° above the horizontal. The ratio of the acceleration of A to that of B is

Accepted Answer

A)  greater than 1. 
B)  equal to 1. 
C)  less than 1. 
D)  zero. 
E)  unknown; more information is needed to work out the answer.

Question 2

A boat travels at a constant speed with respect to still water. The water is moving with respect to the bank at a speed almost as large as the speed of the boat with respect to still water. Assume a round trip of constant distance (with respect to the bank) in the boat under two scenarios: downstream, then upstream or cross-stream, then back. All of the following statements are correct except

Accepted Answer

A)  the speed of the boat when returning upstream is very small. 
B)  the cross-stream scenario involves a cross-stream component that is small, but much larger than the upstream speed of the boat. 
C)  the cross-stream time is independent of the stream speed compared to the boat speed. 
D)  the time spent traveling downstream is very small compared to other travel times in the problem.

Question 3

An airplane having a speed relative to the air of 250 km/h needs to land in a city north of the departure airport when the wind blows toward the east at 40 km/h. The pilot should maintain a heading of

Accepted Answer

A)  79.9°. 
B)  10.1°. 
C)  0°. 
D)  10.2°. 
E)  79.8°.

Question 4

A school bus travels east at 10 km/h. Alex, sitting in the back of the bus throws a tennis ball at Brendan. Kyle, standing next to the road, observes the ball moving at 60 km/h south. The direction of the velocity of the ball with respect to the bus is

Accepted Answer

A)  91° east of north. 
B)  91° west of south. 
C)  81° east of north. 
D)  9.5° west of south. 
E)  9.5° east of north.

Question 5

A boy is shooting marbles on a flatcar that is itself in uniform motion on a straight, horizontal track. The boy can shoot marbles at a speed of 30 m/s with respect to the flatcar. The speed of the flatcar with respect to the train track rails is 40 m/s. The maximum possible horizontal speed of a marble with respect to the rails is

Accepted Answer

A)  10 m/s. 
B)  30 m/s. 
C)  40 m/s. 
D)  50 m/s. 
E)  70 m/s.

Question 6

If reference frame A is in motion with respect to reference frame B, the velocity of an object with respect to frame A

Accepted Answer

A)  cannot equal the velocity of the object with respect to frame B. 
B)  may or may not equal the velocity of the object with respect to frame B. 
C)  must equal the velocity of the object with respect to frame B. 
D)  None of the previous answers is correct.

Question 7

You want to aim a water gun so that the water travels the maximum horizontal distance. The angle you aim at is

Accepted Answer

A)  0o. 
B)  30o. 
C)  45o. 
D)  60o. 
E)  90o.

Question 8

A school bus travels east at 40 km/h. Alex, sitting on the left side of the bus, throws a tennis ball at 30 km/h to Brendan, who is seated on the right side of the bus, directly across from Alex. The velocity of the ball as seen by Kyle, standing next to the road, is

Accepted Answer

A)  26 km/h, 46° east of north. 
B)  26 km/h, 44° east of north. 
C)  10 km/h, 54° east of north. 
D)  50 km/h, 59° east of north. 
E)  50 km/h, 31° east of north.

Question 9

Consider two projectiles A and B launched at angles 30o and 60o from the horizontal with equal initial speeds. All of the following statements are correct except

Accepted Answer

A)  the flight time of A is less than the flight time of B. 
B)  the range of A is less than the range of B. 
C)  the maximum height reached by A is less than the maximum height reached by B. 
D)  the maximum vertical velocity component of A is less than the maximum vertical velocity component of B.

Question 10

A car travels around a curve of constant radius at a constant speed. The direction of the car's centripetal acceleration is

Accepted Answer

A)  horizontal. 
B)  vertical. 
C)  tangent to the curve, and points in the same direction as the car is moving. 
D)  radially inward. 
E)  unknown; more information is needed to work out the answer.

Question 11

A ball is rolling on a table in a partial hoop (shown here as seen looking down on the tabletop). The path of the ball after it leaves the hoop is best described by which of the following arrows?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D

Question 12

A ball leaves the hand of a boy with a velocity v and travels a horizontal range R. In a second throw, the same ball leaves the boy's hand with a velocity of 2v. Compared to the first throw, the horizontal range is

Accepted Answer

A)  the same. 
B)  two times larger. 
C)  half as large. 
D)  four times larger. 
E)  a fourth of the first.

Question 13

A boy runs around a circular track of constant radius at an increasing speed. The magnitude of his centripetal acceleration

Accepted Answer

A)  decreases. 
B)  increases. 
C)  is zero. 
D)  is unknown; more information is needed to work out the answer.

Question 14

A car travels due east with a speed of 40.0 km/h. Raindrops are falling at a constant speed of 30.0 km/h vertically with respect to the Earth. The traces of the rain on the side windows of the car make an angle of

Accepted Answer

A)  53.0° with the vertical. 
B)  53.0° with the horizontal. 
C)  0.0° with the vertical. 
D)  0.0° with the horizontal.

Question 15

A pilot drops a package of food and water supplies from a plane that is flying horizontally at constant speed. When the package reaches the ground, the plane's horizontal position relative to the package

Accepted Answer

A)  is directly above the package. 
B)  is behind the package. 
C)  is in front of the package. 
D)  depends on the mass of the package. 
E)  is unknown; more information is needed to work out the answer.

Question 16

An athlete throws a javelin at four different angles (20o, 30o, 50o, and 70o) above the horizontal, all with the same initial speed. For which two angles will the javelin land at the same distance from the throwing point?

Accepted Answer

A)  20o and 70o 
B)  20o and 50o 
C)  20o and 30o 
D)  30o and 50o 
E)  30o and 70o

Question 17

Two racquets hit two tennis balls at the same speed and angle-one on the Earth and the other on the Moon. Because the acceleration due to gravity on the Moon is six times smaller than on the Earth, the ball on the Moon would travel

Accepted Answer

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

Question 18

A toy car, initially moving along the y axis at 5.00 m/s, is accelerated uniformly for 10.0 s at 2.00 m/s2 along the x axis. The magnitude of the toy car's displacement at the end of the 10.0 s is

Accepted Answer

A)  50.0 m. 
B)  100 m. 
C)  112 m. 
D)  150 m.

Question 19

A car travels on a circular track with a constant speed. The acceleration of the car is

Accepted Answer

A)  directed forward in the direction of travel. 
B)  directed toward the center of the track. 
C)  directed toward the center of the Earth. 
D)  zero because the car travels at constant speed. 
E)  none of the above.

Question 20

If the initial speed of a projectile is doubled, its time of flight would

Accepted Answer

A)  be four times smaller. 
B)  be two times smaller. 
C)  remain unchanged. 
D)  be two times larger. 
E)  be four times larger.

Exam 4: Motion in Two and Three Dimensions