Physics                                                         Name _____________________________  Chapters 9-11

1.        A 130.0 kg roller derby player skates at 30.0 m/s east toward another roller.  The other roller has a         mass of 110.0 kg and skates west at 23.0 m/s.  They collide and become entangled as one mass.  What velocity do they have?

2.        A 30.0 gram ball is thrown at 25.0 m/s at a 200.0 gram bowling pin at rest.  The ball hits the pin and rebounds backward at 5.0 m/s.  What does the velocity of the bowling pin become?

3.        A 65.0 kg boy runs at 2.5 m/s.  How fast would a 42.0 kg girl need to run to have the same         momentum?

4.        A 39.0 kg cheerleader is tossed 3.00 meters into the air by her teammates.  

        a) What is her velocity just as she returns to their arms?

        b) What is her momentum as she returns to their arms?

        c) What impulse is needed to bring her to rest?

        d) Suppose they catch her and bring her to rest over 0.200 seconds.  What force is exerted on the         cheerleader?

5.        The cable from a crane lifts a 3500.0 kg load of steel vertically 75.0 meters in 3.00 minutes.

        a) How much work is done by the cable?

        b) How much power does the cable develop?

6.        An object has a mass of 4500.0 kg.  How much kinetic energy does it have if it’s moving with a         speed of 35.0 km/h?

7.        A horse pulls a 350.0 kg wagon horizontally 120.0 meters.  The horse pulls with a force of         700. N at 15.0º.  How much work does the horse do?

8.        A 25.0 kg dog sprints down the stairs to a floor 2.50 meters below.  How much potential energy         does the dog lose?

9.         A little red wagon starts from rest at the top of a hill 50.0 meters above the ground.  At the         bottom of the hill there is a bridge and the wagon is 3.00 meters above the ground.  What is the speed of the wagon at the bottom of the hill?

10.        A 20.0 kg penguin stands at the edge of an iceberg 25.0 meters above the water.

        a) How much potential energy does the penguin have relative to the water?

        b) The penguin falls in.  How much kinetic energy does it have right before it strikes the water?

        c) What is the penguin’s speed right before it strikes the water?

1.) 5.71 m/s, east; 2.) 4.50 m/s; 3.) 3.87 m/s; 4.) a. -7.67m/s, b. -299 kg-m/s, c. 299 Ns, d. 1.50X103 N;     5.) a. 2.57X106 J, b. 14,300 W; 6.) 213,000 J; 7.) 81,100 J; 8.) -613 J (or 613 J lost); 9.) 30.4 m/s;          10.) a. 4.90x103J, b. 4.90X103J, c. 22.1 m/s