Physics 213 Test 2 12 pts each Oct. 21, 2005

(4 points absolutely free!)

1. Young David who slew Goliath experimented with a couple of slings before tackling Goliath. He found that he could revolve a sling of length 0.6 m at a rate of 8 rev//s. If he increased the length to 0.9 m he could revolve the sling only 6 times a second. Which rate of rotating gives the greater speed of the stone at the end of the sling?

2. A man weighs 900 N on earth. What would he weigh on Jupiter, where the acceleration due to gravity is 30 m/s² ?

3. A ball is tossed from an upper story window of a building . The ball is given an initial velocity of 8 m/s at an angle of 37° below the horizontal. It strikes the ground 3 seconds later. How far horizontally from the base of the building does the ball strike the ground?

4. A coin placed 30 cm from the center of a rotating horizontal turntable slips when its speed reaches 50 cm/s. What is the coefficient of static friction between coin and turntable?

5. A force F = (6 - 2)N acts on a particle that undergoes a displacement Dr = 3 + ) m . What is the work done by the force on the particle?

6. A particle is subject to a force F_x that varies with position as indicated in the figure below. Find the work done on the particle as it moves from x = 0 to x = 10 m.

7. If it takes 4 J of work to stretch a Hooke's law spring 10 cm from its unstretched position, determine the extra work required to stretch it an additional 10 cm.

8. You are travelling in your 2000 kg Chevy at 20 m/s up a hill with a 6° incline when you see a goose crossing the road in front of you. You hit the brakes when the goose is 24 m away. You know from previous experience that when you hit the brakes, a 16000 N friction force opposes your motion. Will you hit the goose?