FINAL EXAM Flashcards
What is Newton’s 1st Law of motion?
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.
What is Newton’s 2nd Law of motion?
What is Newton’s 3rd Law of motion?
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
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
A. equal and in the opposite direction as the man’s push.
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.
B. There is no net force.
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
A. Yes
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.
A. Greater than your true weight
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.
C. Greater than the coefficient of kinetic friction.
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.
B. The drag force will quadruple.
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
C. n is less than mg
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?
No
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.
E. Slows steadily until it stops.
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)
E. 20 sin ϴ (in N)
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.
C. You continue moving even after the car has stopped.
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.
B. The floor deforms—very slightly—under your weight.
An elevator, lifted by a cable, is moving upward and slowing. What is the correct free-body diagram?
A car is parked on a hill. What is the correct free-body diagram?
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
A. equal and in the opposite direction as the man’s push.
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.
C. Both are the same amount.
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.
B. you pulling Earth upward.
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
A. Yes
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.
C. masses are different.
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.
B. There is no net force.
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.
D. Points down at all times.
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.
B. Points toward the center of the circle.
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?
5 m/s
Consider the two cars movements below.
Both have the same time interval between photos. Which car, A or B, is going slower?
A
How many significant figures does this number have?
0.00673
3
How many significant figures does this number have?
0.9510
4
Which position diagram shows a car slowing down?
Remember, the car positions are taken at equal time intervals.
C
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?
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?
The graph below is a velocity versus time for a hockey puck shot into a goal. What position graph matches the velocity graph?
A ball moves to the left and is slowing down. What is the sign of acceleration?
A. Positive
B. Negative
A. Positive
In rotational motion, θ is positive when measured [ ] from the positive x-axis.
counterclockwise (CCW)
In rotational motion, θ is negative when measured [ ] from the positive x-axis.
clockwise (CW)
In rotational motion, which unit represents arc length?
The arc length, s, is the distance that the particle has traveled along its circular path.
Define angular velocity (omega, w)
Angular velocity is the angular displacement through which the particle moves each second
1 mi = ? m
1 mi = 1609 m
In rotational motion, how is 1 revolution measured?
2pi
Torque (τ) is the rotational equivalent of
force.
Torque is in units of
newton-meters, N × m.
[ ] is the line starting at the pivot and extending through the point where force is applied.
Radial Line
A torque causes an angular
acceleration.
The moment of inertia is the rotational equivalent of
mass.
What is Newton’s second law of rotation?
If more than one torque acts on a rigid body about a fixed axis, then the sum of the torques equals the moment of inertia times the angular acceleration
Two conditions for static equilibrium on an extended object:
- The net force on the object must be zero.
- The net torque on the object must be zero.
A car is turning a corner at a constant speed, following a segment of a circle.
What force provides the necessary centripetal acceleration?
A. Gravity
B. Normal Force
C. Static Friction
D. Kinetic Friction
C. Static Friction
A ball at the end of a string is being swung in a horizontal circle. What force is producing the centripetal acceleration of the ball?
Gravity
Air resistance
Normal force
Tension in the string
Tension in the string
A ball at the end of a string is being swung in a horizontal circle.
What is the direction of the net force on the ball?
Tangent to the circle
Toward the center of the circle
Away from the center of the circle
There is no net force
Toward the center of the circle
Astronauts on the International Space Station are weightless because
There’s no gravity in outer space.
The net force on them is zero.
The centrifugal force balances the gravitational force.
g is very small, although not zero.
They are in free fall.
They are in free fall.
A passenger on a carnival ride rides in a car that spins in a horizontal circle as shown below.
At the instant shown, which arrow gives the direction of the net force on one of the riders?
A.
B.
C.
D.
D
If an object is rotating clockwise, this corresponds to a ______ angular velocity.
Positive
Negative
Negative
The fan blade is slowing down. What are the signs of ω and α?
ω is positive and α is positive.
ω is positive and α is negative.
ω is negative and α is positive.
ω is negative and α is negative.
ω is positive and α is zero.
ω is negative and α is positive.