Question 1

A car travels to the right at 50 m/s. A bullet is fired to the right from the car at 300 m/s relative to the car. What is the velocity of the bullet as measured by a stationary observer on the ground?

Accepted Answer

$$350\ \mathrm{m/s}$$

Question 2

A plane flies due east at $$500\ \mathrm{mph}$$ relative to the air. The wind blows due south at $$50\ \mathrm{mph}. $$What is the plane's speed relative to the ground?

Accepted Answer

$$502.5\ \mathrm{mph}$$

Question 3

Carlos rides his bike at $$5\ \mathrm{m/s}$$ relative to Amy, who is standing still. Bill drives his car at $$15\ \mathrm{m/s} in $$the same direction. What is Carlos's velocity relative to Bill?

Accepted Answer

$$-10\ \mathrm{m/s}$$

Question 4

A box rides on a truck that speeds up to the right. The box does not slip. Which way does the friction force on the box point?

Accepted Answer

Right

Question 5

A rocket is rising through the air with its engine firing. Air resistance is significant. Which of the following is NOT a force acting on the rocket?

Accepted Answer

Normal force (upward)

Question 6

A ball travels through a curved tube lying flat on a table. After leaving the tube, which path does it follow (ignore friction and air resistance)?

Accepted Answer

It moves in a straight line tangent to the exit

Question 7

Two stretched rubber bands accelerate an object at $$2\ \mathrm{m/s}^2. $$Four equally stretched rubber bands pull an object with twice the mass. What is its acceleration?

Accepted Answer

$$1\ \mathrm{m/s}^2$$

Question 8

Which of the following statements about Newton's third law is correct?

Accepted Answer

The forces are equal in magnitude and opposite in direction

Question 9

A book rests on a table. Earth pulls downward on the book. What is the Newton's third law partner force?

Accepted Answer

The book pulls up on Earth

Question 10

A plane moves right at $$100\ \mathrm{m/s}$$ relative to the ground. A helicopter rises at $$20\ \mathrm{m/s}. $$From the helicopter, what is the plane’s direction and speed?

Accepted Answer

Right and up; more than $$100\ \mathrm{m/s}$$

Question 11

Which of the following is a long-range force?

Accepted Answer

Gravity

Question 12

A box is pulled by two ropes with tensions $$\vec{T}_1$$ and $$\vec{T}_2. $$What is the net force on the box?

Accepted Answer

$$\vec{T}_1 + \vec{T}_2$$

Question 13

A box slides across a level floor after being kicked. Which force does NOT act on the box after the kick (ignore air resistance)?

Accepted Answer

The kick (forward)

Question 14

Which of the following best describes the normal force?

Accepted Answer

A force perpendicular to the surface

Question 15

A frog sits on an inclined surface and does not slip. Which force prevents the frog from sliding down?

Accepted Answer

Static friction

Question 16

Which of the following statements about forces and motion is correct?

Accepted Answer

An object can move in a direction different from the net force.

Question 17

A compressed spring exerts a force on a box. What is the direction of the force?

Accepted Answer

Pushes the box away from the spring

Question 18

A leaf falls from a tree. Which force acts opposite to the direction of motion?

Accepted Answer

Air resistance (drag)

Question 19

A rocket launches vertically. Which force is responsible for its upward acceleration?

Accepted Answer

Thrust

Question 20

If the net force on an object is zero, what can be said about its velocity?

Accepted Answer

It is constant

Relative Motion and Newton's Laws: Study Guide for Physics with Calculus

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