Midterm 1

Question 1

In what direction does free fall acceleration point?

Answer 1

The free-fall acceleration always points down, no matter what direction an object is moving.

Question 2

What does ∆𝑥 represent and what is the graph for uniform motion?

Answer 2

∆𝑥 = change in position

Uniform Motion - Velocity is constant - no Acceleration

Question 3

What is the equation for velocity and its graph in uniform motion?

Answer 3

𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑣 = ∆𝑥/∆𝑡

Uniform Motion means Velocity is constant - no Acceleration

Question 4

What is the equation for acceleration and its graph in uniform motion?

Answer 4

𝐴𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑎 = ∆𝑣/∆𝑡

Uniform Motion - Velocity is constant - no Acceleration

Question 5

What do the graphs of ∆𝑥, velocity, and acceleration look like in non-uniform motion?

Answer 5

Non-Uniform Motion means velocity not constant – Acceleration Constant

Question 6

What produces acceleration?

Answer 6

Change in velocity. Therefore, acceleration is the rate of change of velocity. 𝐴𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑎 = ∆𝑣/∆𝑡

Question 7

How is gravity represented?

Answer 7

Question 8

How is acceleration on a ramp represented?

Answer 8

Question 9

What can the overall motion of the projectile be broken up into?

Answer 9

The overall motion of the projectile can be broken up into a constant velocity in the horizontal direction (uniform motion) and constant acceleration in the vertical direction (free fall).

The motion can then be decomposed in these two directions and can be treated independently of each other.

Question 10

What is a projectile?

Answer 10

A projectile is an object that moves in two dimensions under the influence of gravity only.

Question 11

What is Newton’s 1st Law of motion?

Answer 11

A body at rest remains at rest and a body in motion continues to move at constant velocity along a straight line unless acted upon by an external force.

Question 12

What is Newton’s 2nd Law of motion?

Answer 12

Question 13

What is Newton’s 3rd Law of motion?

Answer 13

For every action force on an object there is a reaction force that is equal in magnitude and opposite in direction. Third Law Force Pairs

Question 14

Name types of force

Answer 14

• Gravitational: 𝑤 = 𝐹⃗ = 𝑚𝑔 S
• Push
• Tension: 𝑇
• Normal: 𝑛
• Friction – Static/Kinetic
• Drag (fluid resistance)
• Thrust:𝐹⃗

Question 15

How does force make an object move?

Answer 15

• Net force on objects is what makes them accelerate.
• For a crate to accelerate, the push must be greater than the frictional force.

Question 16

What is dynamic equilibrium?

Answer 16

An object at rest is in static equilibrium, and an object moving in a straight line at a constant speed is in dynamic equilibrium.

Question 17

When the man pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is

A. equal and in the opposite direction as the man’s push.

B. equal and in the same direction as the man’s push.

C. less than and in the same direction as the man’s push.

D. more than and in the opposite direction as the man’s push

Answer 17

A. equal and in the opposite direction as the man’s push.

Question 18

A skydiver has reached terminal velocity—she now falls at a constant speed, so her acceleration is zero. Is there a net force on her? If so, what is the direction?

A. There is a net force directed upward.

B. There is no net force.

C. There is a net force directed downward.

Answer 18

B. There is no net force.

Question 19

Two people of equal mass on slippery ice are standing still and then push off from each other. Will both move at the same speed in opposite directions?

A. Yes

B. Yes, but only if both push equally.

C. No

Answer 19

A. Yes

Question 20

You are riding in an elevator that is accelerating upward. Suppose you stand on a scale. The reading on the scale is

A. Greater than your true weight.

B. Equal to your true weight.

C. Less than your true weight.

Answer 20

A. Greater than your true weight

Question 21

In general, the coefficient of static friction is

A. Smaller than the coefficient of kinetic friction.

B. Equal to the coefficient of kinetic friction.

C. Greater than the coefficient of kinetic friction.

Answer 21

C. Greater than the coefficient of kinetic friction.

Question 22

The drag force pushes opposite your motion as you ride a bicycle. If you double your speed, what happens to the magnitude of the drag force?

A. The drag force will double

B. The drag force will quadruple.

C. The drag force stays the same.

D. The drag force decreases.

Answer 22

B. The drag force will quadruple.

Question 23

A box is being pulled to the right at steady speed by a rope that angles upward. In this situation:

A. n is greater than mg

B. n is equal to mg

C. n is less than mg

D. n is equal to 0

Answer 23

C. n is less than mg

Question 24

A box with a weight of 100 N is at rest. It is then pulled by a 30 N horizontal force.

The coefficient of static and kinetic friction are listed below.

Does the box move?

Answer 24

No

Question 25

A box is being pulled to the right over a rough surface with tension T, where
T > fk. So the box is speeding up. Suddenly the rope breaks.

What happens? The box

A. Stops immediately.

B. Continues with the speed it had when the rope broke.

C. Continues speeding up for a short while, then slows and stops.

D. Keeps its speed for a short while, then slows and stops.

E. Slows steadily until it stops.

Answer 25

E. Slows steadily until it stops.

Question 26

A ring, seen from above, is pulled on by three forces. The ring is not moving. How big is the force F?

A. 20 N

B. 10 cos ϴ (in N)

C. 10 sin ϴ (in N)

D. 20 cos ϴ (in N)

E. 20 sin ϴ (in N)

Answer 26

E. 20 sin ϴ (in N)

Question 27

If you are not wearing a seat belt and the car you are driving hits a fixed barrier, you will hit the steering wheel with some force. This is because

A. The force of the collision has thrown you forward.

B. The steering wheel has been pushed back toward you.

C. You continue moving even after the car has stopped.

Answer 27

C. You continue moving even after the car has stopped.

Question 28

If you stand on a trampoline, it depresses under your weight. When you stand on a hard stone floor, what happens?

A. The floor does not deform under your weight; it is too stiff.

B. The floor deforms—very slightly—under your weight.

C. The floor deforms a slight amount if you are heavy enough.

Answer 28

B. The floor deforms—very slightly—under your weight.

Question 29

An elevator, lifted by a cable, is moving upward and slowing. What is the correct free-body diagram?

Answer 29

Question 30

A car is parked on a hill. What is the correct free-body diagram?

Answer 30

Question 31

When the man pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is

A. equal and in the opposite direction as the man’s push.

B. equal and in the same direction as the man’s push.

C. less than and in the same direction as the man’s push.

D. more than and in the opposite direction as the man’s push

Answer 31

A. equal and in the opposite direction as the man’s push.

Question 32

Consider a high-speed bus colliding head-on with a flying bug. The force of impact splatters the unfortunate bug over the windshield.

Which is greater, the force on the bug or the force on the bus?

A. Bug

B. Bus

C. Both are the same amount.

Answer 32

C. Both are the same amount.

Question 33

When you step off a curb, Earth pulls you downward. The reaction to this force is

A. slight air resistance.

B. you pulling Earth upward.

C. there is no reaction to this force.

Answer 33

B. you pulling Earth upward.

Question 34

Two people of equal mass on slippery ice are standing still and then push off from each other. Will both move at the same speed in opposite directions?

A. Yes

B. Yes, but only if both push equally.

C. No

Answer 34

A. Yes

Question 35

When a cannon is fired, the accelerations of the cannon and cannonball are different because the:

A. forces don’t occur at the same time.

B. forces, although theoretically the same, in practice are not.

C. masses are different.

D. ratios of force to mass are the same.

Answer 35

C. masses are different.

Question 36

A skydiver has reached terminal velocity—she now falls at a constant speed, so her acceleration is zero. Is there a net force on her? If so, what is the direction?

A. There is a net force directed upward.

B. There is no net force.

C. There is a net force directed downward.

Answer 36

B. There is no net force.

Question 37

The acceleration vector of a particle in projectile motion

A. Points along the path of the particle.

B. Points horizontally at all times.

C. Vanishes at the particle’s highest point.

D. Points down at all times.

E. Is zero.

Answer 37

D. Points down at all times.

Question 38

The acceleration vector of a particle in uniform circular motion

A. Is zero.

B. Points toward the center of the circle.

C. Points outward from the center of the circle.

D. Points tangent to the circle, in the direction of motion.

E. Points tangent to the circle, opposite the direction of motion.

Answer 38

B. Points toward the center of the circle.

Question 39

A factory conveyor belt rolls at 3 m/s. A mouse sees a piece of cheese directly across the belt and heads straight for the cheese at 4 m/s. What is the mouse’s speed relative to the factory floor?

Answer 39

5 m/s

Question 40

Consider the two cars movements below.

Both have the same time interval between photos. Which car, A or B, is going slower?

Answer 40

A

Question 41

How many significant figures does this number have?

0.00673

Answer 41

3

Question 42

How many significant figures does this number have?

0.9510

Answer 42

4

Question 43

Which position diagram shows a car slowing down?

Remember, the car positions are taken at equal time intervals.

Answer 43

C

Question 44

Consider the motion diagram below of a car moving along a straight road. What is the velocity graph that matches the motion of the car?

Answer 44

Question 45

Consider the motion diagram below of a car moving along a straight road. What is the velocity graph that matches the motion of the car?

Answer 45

Question 46

The graph below is a velocity versus time for a hockey puck shot into a goal. What position graph matches the velocity graph?

Answer 46

Question 47

A ball moves to the left and is slowing down. What is the sign of acceleration?

A. Positive

B. Negative

Answer 47

A. Positive