Physics - Unit V Review

**Considering the frictionless situation at left, understand how acceleration might change if one or more of the features change (if mass changes, or force changes) by filling in increases, decreases, stays the same, not enough info to tell. When F answering, consider Newton’s 2nd Law solved for acceleration  a = m

1. If the mass of the cart is cut in half, the acceleration ______

2. If the towing force is decreased to 0.25N, the acceleration ______

3. If the mass and force is decreased by half, the acceleration ______

4. If the force is applied at an angle above the horizontal, the acceleration ______

5. If the track is inclined the acceleration ______

6. If the 0.5 N force is applied to 4 carts (each 0.25kg) all connected together, the acceleration ______

**Given a velocity vs time graph, draw the corresponding a vs t and x vs t graphs. (Unit 3 Stacks of Kinematic Curves, or Unit 3 Kinematic Curves Quiz)

7. For the v vs t graph at right, Section A or C, where is the net force V the smallest & why?

C D B 8. For the graph at right, is there section where net force equals zero? Why? A

**Determine the sum of the forces acting on an object ©Modeling Workshop Project 2006 1 Unit V review v3.0 From dynamics information - If you are given forces, or the physical description of the system and surroundings, draw a force diagram. Ask yourself: "Can I tell if the system is accelerating?" If yes, then the forces do NOT add up to zero. ΣF = ma. If the system is moving at constant velocity or is motionless, then the forces cancel out. ΣF = 0.

9. For system #1: Solve for acceleration. μ = 0.1 the masses are 15kg and 2 kg

10. For system #2: Mass is 10kg, and the frictional force is 2.5N. Draw a rotated force diagram next to it where the normal force is pointing up in the positive Y-axis and the frictional force is pointing in the positive x- direction. What is the value of μ?

11. For system #3: mass is 20kg, pull force is 200N, what is the acceleration?

12. For system #3: if μ = 0.1, what is the acceleration?

a) Express Fx and Fy in terms of the F. (solve for the component)

**Given kinematic information (∆ x, v, t), find the acceleration first, then use F = ma to solve for force. a) A 12, 000 kg bus slows from 30 m/s to 10 m/s in 10 s. What is the net force acting on the bus?

b) What does a scale read for a 75 kg man in an elevator that goes from - 6.0 m/s to zero in 2.0 s ?

**Strategy A 10 kg box is dragged across a horizontal surface ( = 0.20) by a 100 N force that is applied at a 30° angle from the horizontal. Describe how you would go about finding the acceleration of the box. (You can solve the problem mathematically, and then describe step by step, and why you took that step)