1. Quiz A car passes over a hill in the road that has a circular cross-section with a radius of 30m. The speed of the car at the top of the hill is 10 m/s. What is the force exerted by the seat of the car on a 60kg passenger when the car is at the top pf the hill? V

3. Work

5. 1. External force F is applied 2. Object moves through a displacement d Work is done: W = F × d Scalar!!! Work

6. Consider a 1-kg dynamics cart being pulled at angle θ that can roll on a low- friction horizontal dynamics track and a piece of clay that is taped to the fixed, vertical end of the track. You pull the cart so that it rolls faster and faster toward the piece of clay at the end of the dynamics track and squash the clay when it hits it. Draw the force exerted by you on the cart and the displacement of the cart while you were pulling it. b) Discuss whether the angled force exerted on the cart while moving it horizontally gave it a better chance of breaking the piece of chalk than the force exerted in activity 1.1 part (b). c) What trigonometric function would help you determine the system’s increase in “clay-squashing” ability? Is this consistent with the increase, decrease, and no change in chalk-smashing potential for activities 1.1-1.3?

7. Work

8. Positive and Negative Work F d θ W = F d cosθ F d θ F dθ > 0 = 0 < 0

9. Work Very short kick F = 200N AB C You gave a very short kick with force F = 200N to a bowling ball at point A. The ball started rolling along a straight line. a) How much work has been done by force F trough a distance D between points B and C. b) What work has been done by kick force at moment of the kick. D = 1meter W = F d cosθ

10. While working out, a man lifts with constant speed a 10-kg object a vertical distance of 0.80 m. How much work does he do on the object when he picks the object up. 0.8m F =? 10 kg mg = 100 N W =?mgh = 100N × 0.8m = 80 N×mJoule

11. While working out, a man lifts a 10-kg object a vertical distance of 0.80 m. He then carries it for 10 m where he sets it down a vertical distance of 0.80 m. How much work does he do on the object when he picks the object up, when he carries it, and when he sets it back down? What is the total work that he does on it? 0.8m 10 kg 10m

12. Conservative Forces 6cm 4cm 2cm

13. You want to load a box into the back of a truck. One way is to lift it straight up through a height h, doing work W1. Alternatively, you can slide the box up a loading ramp a distance L, doing work W2. Assuming that the box slides on the ramp without friction which of the following is correct (a) W1 < W2, (b) W1 = W2, (c) W1 > W2?

14. Energy

15. Energy Bar charts Work-energy bar charts provide a concrete way to represent work-energy processes. In a work-energy bar chart, a bar represents each type of energy initially in the system, as well as the final energies of the system. If external objects do work on the system (positive or negative), then there is a bar to represent work. We don’t know the exact amount of energy or work usually but we can still make estimates based on the situation. The column for the work bar is shaded to indicate that it is not a type of energy but is instead a process involving an interaction between a system object and an object outside the system. 0 + - Before After KiKi U gi U si KiKi U gi U si U int W

16. Quiz

17. No Homework!!! No Quiz!!!