Physics 201 MWF10:20 Fall 2002 (Ford)

Exam II Chapts 5--7 Cutnell and Johnson 5th ed


Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.

(18 pts) 1. James Bond has a propulsion unit strapped on his back. He starts from rest on the ground, turns on the unit, and is propelled into the air. His mass, including the propulsion unit, is 150 kg. During his motion from the ground to a height of 20 m the force the propulsion unit exerts does 45,000 J of work on him. Neglect any effects of air resistance. What is his speed when he reaches the height of 20 m?

Ans.___14.4m/s_____


(20 pts) 2. A motorcycle has constant speed v as it passes over the top of a hill that has the shape of an arc of a circle with radius 80 m. The combined mass of the motorcycle and rider is 200 kg.



a) If the normal force that the ground exerts on the motorcycle at the top of the hill is 800 N, what is the speed v of the motorcycle?

Ans.___21.5 m/s_____

b) What is the minimum speed v for which the motorcycle loses contact with the ground at the top of the hill?

Ans. _____28 m/s___


(22 pts) 3. A 0.20 kg rock is projected up a metal track as shown in the sketch. At point A the rock has speed 20 m/s and at point B the rock has speed 15 m/s. Point B is a vertical distance 6.0 m above point B. How much work was done by friction as the rock traveled from point A to point B?



Ans. ___-5.7 J___


(20 pts) 4. On a level horizontal surface a 1.0 kg block hits a 4.0 kg block and sticks to it. After the collision the two blocks slide 3.0 m before coming to rest. The coefficient of kinetic friction between the blocks and the surface is 0.30. Just before the collision the 4.0 kg block is at rest. What was the speed of the 1.0 kg block just before it hit the 4.0 kg block?



Ans. ____21 m/s___


(20 pts) 5. Two people are sliding together in the +x-direction with a speed of 8.0 m/s on a horizontal frictionless surface. Suddenly one person pushes against the other and they move apart. One person has mass 60 kg and ends up moving with a speed of 12 m/s in a direction of 37° from the +x-axis, as shown in the sketch. The second person has mass 40 kg. What is the final speed of the second person?

Ans. ____12.2 m/s____