Physics Chapter Four

Objects A and B both move with constant acceleration along the x-axis. Object A has a velocity of 10 m/s and an acceleration of 0 m/s2 when it passes object B, which is rest at the origin at t = 0 s. If object B has an acceleration of 2 m/s2 and starts moving the instant object A passes it, which object crosses the finish line at x = 100 m first? A Not enough information is given to answer the question. B A and B cross the finish line at the same time.

A and B cross the finish line at the same time.

Consider the motion of a projectile launched horizontally. Which of the motion diagrams shown represents the horizontal motion of the projectile? Case B, D, A, C

B

Four trajectories are shown. Select all of the cases that are consistent with projectile motion. Case B Case C Case D Case A

Case B Case D

Consider the motion of a projectile launched horizontally. Which of the motion diagrams shown represents the vertical motion of the projectile? Case B,A,D,C

Case C

An object in free-fall never moves upward. True or false:

False

True or false: If an object is in free-fall, then its acceleration is zero when it is located at its highest point. True or False

False

Select all of the following that describe the force of air resistance. It is always in the opposite direction of the velocity. It is always in the same direction as the velocity. It depends on speed. It does not depend on speed.

It is always in the opposite direction of the velocity. It depends on speed.

An object is in free-fall. What are the object's velocity and acceleration when it is located at its highest point? Its acceleration is zero, but its velocity is not zero. Both its velocity and acceleration are not zero. Its velocity is zero, but its acceleration is not zero. Both its velocity and acceleration are zero.

Its velocity is zero, but its acceleration is not zero.

Rank the following situations in terms of the apparent weight of a person who is riding in an elevator, with the largest apparent weight at the top and the smallest at the bottom.

The elevator is moving downward with decreasing speed The elevator is moving upward at constant velocity The elevator is moving upward with decreasing speed

Select all of the following that describe projectile motion. The motion is only influenced by gravity. The motion is along one straight line. The acceleration of the object is in the vertical direction. The object accelerates both horizontally and vertically.

The motion is only influenced by gravity. The acceleration of the object is in the vertical direction.

Object A is thrown upward with a velocity of 5 m/s. Object B is thrown downward with a velocity of -5 m/s. If both objects are thrown from the same height above the floor, which one will be moving faster when it hits the floor? Object A will be moving faster. Object B will be moving faster. They will be moving at the same speed.

They will be moving at the same speed.

If the acceleration is constant, then the acceleration multiplied by the time interval gives the change in __________

Velocity

An apple falls from a tree through the Earth's atmosphere. Is the apple in free-fall? No, because the apple is accelerating. Yes, if air resistance is negligibly small. Yes, if the apple is falling at constant velocity. No, because the apple is moving. Yes, if the gravitational pull of the Earth is negligibly small.

Yes, if air resistance is negligibly small.

The following equation is only true for constant vav,x = 1/2 (vfx + vix) (constant ax)

acceleration

Which of the following could be the equation for the trajectory of a projectile? Both x and y are measured in meters. The x-axis is horizontal and the y-axis is vertical. y = 4x y = 4x + (20 m) x = (1/(18 m))y2 + (2 m) y = (- 1/(4 m)) x2 - (18 m)

y = (- 1/(4 m)) x2 - (18 m)

What is the apparent weight of a person of mass m in a gravitational field g while in free fall? zero mg g m

zero NOTES: N=mg-ma=0

Object A, initially at rest, is dropped from a height of 20 m above the floor the instant object B is thrown upward from a height of 10 m above the floor. What must be the approximate initial velocity of object B for it to strike the floor at the same time that object A does? 7.0 m/s 1.0 m/s 4.9 m/s 2.0 m/s 4.0m/s

4.9m/s

Choose the situations for which the following equation can be used to find the average velocity. vav,x = 12 (vfx + vix) (constant ax) Driving one leg of a journey at one velocity and the second leg at a different velocity Slowing to a stop while approaching a stoplight with constant acceleration While smoothly speeding up to highway speeds on an entrance ramp

Slowing to a stop while approaching a stoplight with constant acceleration While smoothly speeding up to highway speeds on an entrance ramp

For the following statement, match the letter of the missing word in the left column with the missing word in the right column. A motion diagram for projectile motion should show the horizontal spacing of the object to be WORD-A, and the vertical spacing of the object to be WORD-B.

WORD A --> Uniform WORD B --> Nonuniform

For the following statement, match the letter of the missing word in the left column with the missing word in the right column. A motion diagram for projectile motion should show the horizontal velocity components to be WORD A, and the vertical velocity components to be WORD B.

WORD A = Constant Word B = changing

When is the maximum height of an ideal projectile equal to its initial vertical position? When the projectile is launched vertically upward When the projectile is launched downward at some angle with respect to the horizontal When the projectile is launched upward at some angle with respect to the horizontal

When the projectile is launched downward at some angle with respect to the horizontal

Choose the situations for which the following equation can be used to find the average velocity. vav,x = 12 (vfx + vix) (constant ax) Driving one leg of a journey at one velocity and the second leg at a different velocity While smoothly speeding up to highway speeds on an entrance ramp Slowing to a stop while approaching a stoplight with constant acceleration

While smoothly speeding up to highway speeds on an entrance ramp Slowing to a stop while approaching a stoplight with constant acceleration NOTES: The only way this would work would be if the two legs took the same amount of time. Otherwise, this would not give you the average velocity.

Which of the following describes a projectile with the greatest initial velocity in the y-axis? y = (1/2)*t^2 - 4t + 3 y = (1/2)*t^2 + 4t + 4 y = (1/2)*t^2 + 5t + 3 y = (1/2)*t^2 + 4t + 3

y = (1/2)*t^2 + 5t + 3

Objects A and B are moving toward each other along the x-axis with constant velocities of vx = 5 m/s and vx = -4 m/s, respectively. They collide at t = 5 s. If object B was at the origin at t = 0 s, then what was the x-coordinate of object A at t = 0 s? 20 m -100 m -45 m

-45 m Object B moved (5 s)(-4 m/s) = -20 m and object A moved (5 s)(5 m/s) = 25 m. So, object A must have started at -20 m - 25 m = -45 m.

A car starts from rest and moves with constant acceleration over a certain distance d. Its final speed is 10 m/s. What would be its final speed if it started from rest and moved with the same constant acceleration as before over twice the distance 2d? 20 m/s 10 m/s 40 m/s 14 m/s

14 m/s

An object is dropped from a height of 10 m above the floor. Approximately how fast is it going just before it hits the floor? 10 m/s 20 m/s 14 m/s 98 m/s

14m/s

An object starts at rest at the origin at t = 0 s. It travels 100 m in the +x-direction in 10 s at constant acceleration. What was the magnitude of its acceleration? 2 m/s2 1 m/s2 10 m/s2

2 m/s2 NOTES: Use a kinematic equation with both initial position and initial velocity equal to zero.

A car starts from rest and moves with constant acceleration during a certain time interval Δt. Its final speed is 20 m/s. What would be its final speed if it started from rest and moved with the same constant acceleration during twice the time interval 2Δt? 20 m/s 10 m/s 40 m/s 14 m/s

40 m/s

For projectile motion, how is the angle of elevation defined? Angle of the final velocity above the horizontal Angle of acceleration below the horizontal Angle of the initial velocity below the horizontal Angle of the initial velocity above the horizontal Angle of acceleration above the horizontal Angle of the final velocity below the horizontal

Angle of the initial velocity above the horizontal

A stone is thrown from the ground at an angle to the horizontal and falls back to the ground. A graph of the vertical component of its velocity versus time is shown. Select all points on the graph that correspond to the stone traveling downward. C B A E D

E D

Identical boxes are at rest on six planes inclined at different angles. Rank the planes (denoted by their incline angles) according to the static friction force the plane exerts on the box, with the largest friction force on the top and the smallest on the bottom. The coefficients of static friction are 1 for A and F, 3 for B and E, and 2 for C and D.

E, C, A, D, B, F

The diagram shows the trajectory of a soccer ball during a game with the +y-axis up. Select all of the following that could be the soccer ball's vertical acceleration component ay. Greater than 0 m/s2 Equal to 0 m/s2 Equal to -9.8 m/s2 Less than 0 m/s2

Equal to -9.8 m/s2 Less than 0 m/s2

The diagram shows the trajectory of a soccer ball during a game. What is the soccer ball's horizontal acceleration? Air resistance is negligible. Equal to 0 m/s2 Less than 0 m/s2 Greater than 0 m/s2

Equal to 0 m/s2

Two boxes, A and B, are being pushed to the right by applying a force F→ on box A, as shown. The acceleration is to the right. The coefficient of kinetic friction for box A sliding along the floor is the same as that of box B sliding along the floor, and it is less than 1. The mass of box B is greater than that of box A. Rank the following forces from greatest magnitude on the top to smallest magnitude on the bottom

F --> Force of A on B Kinetic friction force on B Kinetic friction force on A

Select all the cases for which the following equation is valid. Δvx = vfx - vix = axΔt If the velocity changes linearly If the acceleration is given for a specific moment even though it is changing If we know the average acceleration If the acceleration is constant

If the velocity changes linearly If we know the average acceleration If the acceleration is constant

What is the trajectory of a projectile? Parabola Horizontal line Vertical line Diagonal line Circle

Parabola

The acceleration of an object moving along a straight line is constant. Select all of the possible shapes for the graph of its velocity versus time. Parabola opening downward Semicircle not passing through the origin Straight line passing through the origin Parabola opening upward Straight line not passing through the origin Semicircle passing through the origin Horizontal line

Straight line not passing through the origin Straight line passing through the origin Horizontal line

The acceleration of an object moving along a straight line is constant. Select all of the possible shapes for the graph of its position versus time. Semicircle passing through the origin Straight line passing through the origin Parabola opening downward Parabola opening upward Straight line not passing through the origin Semicircle not passing through the origin

Straight line passing through the origin Parabola opening downward Parabola opening upward Straight line not passing through the origin

During each time interval on a motion diagram, the magnitudes of the displacements are decreasing. If the object is moving in the positive x-direction, then what is the acceleration? The acceleration is in the negative x-direction. The acceleration is zero. The acceleration is in the positive x-direction.

The acceleration is in the negative x-direction Notes: The speed is decreasing in the positive x-direction, so the acceleration is in the negative x-direction.

During each time interval on a motion diagram, the magnitudes of the displacements are increasing. If the object is moving in the positive x-direction, then what is the acceleration? The acceleration is in the negative x-direction. The acceleration is zero. The acceleration is in the positive x-direction.

The acceleration is in the positive x-direction. NOTES: The speed is increasing in the positive x-direction, so the acceleration is in the positive x-direction.

During each time interval on a motion diagram, the magnitudes of the displacements are constant. If the object is moving in the positive x-direction, then what is the acceleration? The acceleration is in the negative x-direction. The acceleration is zero. The acceleration is in the positive x-direction.

The acceleration is zero. NOTES: The velocity is constant, so the acceleration is zero.

Select all of the following that correspond to the condition of terminal velocity. The acceleration is zero. The force of air resistance is in the same direction as the force of gravity. The magnitude of the force of air resistance is equal to the magnitude of the force of gravity.

The acceleration is zero. The magnitude of the force of air resistance is equal to the magnitude of the force of gravity.

The trajectory of an object is shown. Select all of the following that explain why the range and the horizontal displacement are unequal. The range includes only the part of the trajectory for which the vertical displacement is equal to zero. The range and the horizontal displacement are equal for all projectile motion. The initial and final vertical positions are unequal.

The range includes only the part of the trajectory for which the vertical displacement is equal to zero. The initial and final vertical positions are unequal.

A projectile is launched from the ground. Its initial velocity is up and to the right. It travels over flat, level ground until it lands. Select all of the following statements that are true. The range of this projectile is equal to the horizontal displacement. The range of the projectile is equal to the entire vertical distance traveled. The range of the projectile is equal to the entire horizontal distance traveled. The range of this projectile is equal to zero. The range of the projectile is equal to the entire vertical displacement.

The range of this projectile is equal to the horizontal displacement. The range of the projectile is equal to the entire horizontal distance traveled.

For the following statement, match the letter of the missing word in the left column with the missing word in the right column. A motion diagram for projectile motion should show the horizontal velocity components to be WORD A, and the vertical velocity components to be WORD B. WORD A WORD B

WORD A --> changing WORD B--> Constant

An object has an initial velocity shown. In which of the stated directions could a nonzero constant acceleration be applied so that the object moves with projectile motion? left right up down

down