Force Concept review

Force Concept Review

Unit IV - The Force ConceptNewton's 1st Law1.What can you conclude about the forces on an object when it is moving at constant velocity?

The sum of the forces is Zero, F = 0

2.Describe the motion of an object when the sum of the forces on it is zero.(2 cases)1. The object is motionless, V=0 so no Acc. 2. The object is moving at a constant velocity

3.State Newton's 3rd Law. All forces come in pairs, paired forces are:

a. Equal in magnitude

b. Opposite in sign

c. Act on separate bodies

When a bug collides with a windshield, it experiences a greater effect than does the car. How can Newton's 3rd Law be correct in this case?Bug F = m A same force on both, but different accelerationsCar F = M a

Unit V - Newton's 2nd Law4.How can you distinguish constant speed and uniform acceleration?Acceleration is CHANGE in velocity, either speed or directionConstant speed has no change in either speed or direction

5.How can an object be moving to the right, yet have a negative acceleration?

The object is slowing down so the change in velocity is negative

6.State Newton's 2nd Law.F = MA

Unit VI - 2-D Motion7.Describe the path a projectile takes when air resistance is neglected.The path is parabolic .

8.You throw a ball to your friend. Draw a force diagram for the ball when it is in the air.

The downward gravitational force is the only force acting on the ball (assuming no air resistance)

9.Describe the motion of the ball in the x-direction. Explain in terms of forces.

The horizontal motion is constant velocity, there is no net force

10. Describe the motion of the ball in the y-direction. Explain in terms of forces.

The vertical motion is acceleration, there is a net force downward from gravity

Unit VIII - Uniform Circular Motion11. Explain how an object moving a circle can have constant speed, yet always be accelerating.

The speed is constant, but the direction is constantly changing so there is a change in velocity. V = acc.

12. What is the direction of acceleration of a coaster when it is at the bottom of a vertical loop? at the top of the loop?

Always towards the center of the circle, at the bottom it is upward, at the top it is downward

13. Describe how the motion of an object in UCM changes when the centripetal force goes to zero.There is no net force, so no acceleration. The object moves at a constant speed tangent to the circle