﻿ ﻿Review Questions - Kinematics - SAT Physics Subject Test

## Chapter 2 Kinematics

### Chapter 2 Review Questions

See Chapter 17 for solutions.

1. An object that”s moving with constant speed travels once around a circular path. True statements about this motion include which of the following?

I. The displacement is zero.

II. The average speed is zero.

III. The acceleration is zero.

(A) I only

(B) I and II only

(C) I and III only

(D) III only

(E) II and III only

2. At time t = t1, an object”s velocity is given by the vector v1 shown below. A short time later, at t = t2, the object”s velocity is the vector v2. If v1 and v2 have the same magnitude, which one of the following vectors best illustrates the object”s average acceleration between t = t1 and t = t2 ?

(A) (B) (C) (D) (E) 3. Which of the following must always be true?

I. If an object”s acceleration is constant, then it must move in a straight line.

II. If an object”s acceleration is zero, then its speed must remain constant.

III. If an object”s speed remains constant, then its acceleration must be zero.

(A) I and II only

(B) I and III only

(C) II only

(D) III only

(E) II and III only

4. A baseball is thrown straight upward. What is the ball”s acceleration at its highest point?

(A) 0

(B) g, downward

(C) g, downward

(D) g, upward

(E) g, upward

5. How long would it take a car, starting from rest and accelerating uniformly in a straight line at 5 m/s2, to cover a distance of 200 m ?

(A) 9.0 s

(B) 10.5 s

(C) 12.0 s

(D) 15.5 s

(E) 20.0 s

6. A rock is dropped off a cliff and strikes the ground with an impact velocity of 30 m/s. How high was the cliff?

(A) 15 m

(B) 20 m

(C) 30 m

(D) 45 m

(E) 60 m

7. A soccer ball, at rest on the ground, is kicked with an initial velocity of 10 m/s at a launch angle of 30°. Calculate its total flight time, assuming that air resistance is negligible.

(A) 0.5 s

(B) 1 s

(C) 1.7 s

(D) 2 s

(E) 4 s

8. A stone is thrown horizontally with an initial speed of 30 m/s from a bridge. Find the stone”s total speed when it enters the water 4 seconds later. (Ignore air resistance.)

(A) 30 m/s

(B) 40 m/s

(C) 50 m/s

(D) 60 m/s

(E) 70 m/s

9. Which one of the following statements is true concerning the motion of an ideal projectile launched at an angle of 45° to the horizontal?

(A) The acceleration vector points opposite to the velocity vector on the way up and in the same direction as the velocity vector on the way down.

(B) The speed at the top of the trajectory is zero.

(C) The object”s total speed remains constant during the entire flight.

(D) The horizontal speed decreases on the way up and increases on the way down.

(E) The vertical speed decreases on the way up and increases on the way down.

Keyword

kinematics

displacement

velocity

average speed

average velocity

speed

acceleration

average acceleration

uniform acceleration

launch angle

range

free fall

Summary

· Displacement is the vector that connects an object”s initial position with its final position. It is the net distance traveled.

· Distance is the length of the particular path chosen (a scalar).

· Speed is a scalar quantity and is always taken as a positive.

· Velocity is a vector that embodies speed and direction and measures the rate of change of an object”s position.

· Acceleration measures the rate of change of an object”s velocity.

· For cases in which acceleration is uniform, use the Big Five equations to find the missing variable that represents acceleration, displacement, initial velocity, final velocity, or elapsed time. Memorize the chart on this page.

· The two most popular graphs in kinematics are the position-versus-time graph and the velocity-versus-time graph. The slope of a position-versus-time graph gives the velocity, while the slope of a velocity-versus-time graph gives the acceleration.

· On a velocity-versus-time graph, the area between the graph and the t-axis is equal to the object”s displacement.

· Gravitational acceleration has a constant magnitude of about 9.8 m/s2. Use 10 m/s2 when you estimate.

· Since gravitational acceleration is constant, it can be replaced by either +g or −g with a + sign if down is the positive direction and a – sign if down is the negative direction. By default, take the direction of an object”s displacement as positive.

· Projectile motion is the parabolic path caused by the pull of gravity on an object moving near the surface of the earth.

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