Midterm 1 Flashcards
In what direction does free fall acceleration point?
The free-fall acceleration always points down, no matter what direction an object is moving.
What does โ๐ฅ represent and what is the graph for uniform motion?
โ๐ฅ = change in position
Uniform Motion - Velocity is constant - no Acceleration
What is the equation for velocity and its graph in uniform motion?
๐๐๐๐๐๐๐ก๐ฆ = ๐ฃ = โ๐ฅ/โ๐ก
Uniform Motion means Velocity is constant - no Acceleration
What is the equation for acceleration and its graph in uniform motion?
๐ด๐๐๐๐๐๐๐๐ก๐๐๐ = ๐ = โ๐ฃ/โ๐ก
Uniform Motion - Velocity is constant - no Acceleration
What do the graphs of โ๐ฅ, velocity, and acceleration look like in non-uniform motion?
Non-Uniform Motion means velocity not constant โ Acceleration Constant
What produces acceleration?
Change in velocity. Therefore, acceleration is the rate of change of velocity. ๐ด๐๐๐๐๐๐๐๐ก๐๐๐ = ๐ = โ๐ฃ/โ๐ก
How is gravity represented?
How is acceleration on a ramp represented?
What can the overall motion of the projectile be broken up into?
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.
What is a projectile?
A projectile is an object that moves in two dimensions under the influence of gravity only.
What is Newtonโs 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 Newtonโs 2nd Law of motion?
What is Newtonโs 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
Name types of force
- Gravitational: ๐ค = ๐นโ = ๐๐ S
- Push
- Tension: ๐
- Normal: ๐
- Friction โ Static/Kinetic
- Drag (fluid resistance)
- Thrust:๐นโ
How does force make an object move?
- Net force on objects is what makes them accelerate.
- For a crate to accelerate, the push must be greater than the frictional force.
What is dynamic equilibrium?
An object at rest is in static equilibrium, and an object moving in a straight line at a constant speed is in dynamic equilibrium.
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 manโs push.
B. equal and in the same direction as the manโs push.
C. less than and in the same direction as the manโs push.
D. more than and in the opposite direction as the manโs push
A. equal and in the opposite direction as the manโs push.
A skydiver has reached terminal velocityโshe 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 ฯด (in N)
C. 10 sin ฯด (in N)
D. 20 cos ฯด (in N)
E. 20 sin ฯด (in N)
E. 20 sin ฯด (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 deformsโvery slightlyโunder your weight.
C. The floor deforms a slight amount if you are heavy enough.
B. The floor deformsโvery slightlyโunder 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 manโs push.
B. equal and in the same direction as the manโs push.
C. less than and in the same direction as the manโs push.
D. more than and in the opposite direction as the manโs push
A. equal and in the opposite direction as the manโs 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 donโt 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 velocityโshe 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 particleโs 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 mouseโs 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
