Question

6. A boulder rests on a ledge 31.2 m above a lake. If it has 2.65 × 105 J of gravitational potential energy relative to the lake surface, what is the mass of the boulder? Show all your work.
7. On a highway, a car with a mass of 1.1 × 103 kg is
travelling at 25 m/s. What is the kinetic energy of the
car? Show all your work.

8. A girl is travelling on her bike at a speed 2.54 m/s. If the
girl and her bike have a kinetic energy of 193 J, what is the combined mass of the girl and her bike? Show all
your work. 9. A hockey puck has a mass of 0.20 kg. If the hockey puck
is moving with 75 J of kinetic energy, what is its speed? Show all your work.


10. a. A 0.430 kg baseball comes off a bat and goes
straight up in the air. At a height of 10.0 m, the
baseball has a speed of 25.3 m/s. Determine the
mechanical energy at this height. Show all your
work.



b. What is the baseball’s mechanical energy when it is at a height of 8.0 m? Explain. 2

11. A golfer hits a 42 g ball, which comes down on a tree root and bounces straight up with an initial speed of 15.6 m/s. Determine the height the ball will rise after the bounce. Show all your work.

12. A girl pushes herself up a steep ramp in her
wheelchair. She gains a vertical distance of
25.8 m when she reaches the top of the ramp.
She turns around and coasts back down the ramp.
If the combined mass of the girl and her wheelchair is 64.6 kg, what would be her coasting speed at the bottom of the ramp? Show all your work.

Answer 1

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• Physics is the branch of science that deals with the structure of matter and how the fundamental constituents of the universe interact. It studies objects ranging from the very small using quantum mechanics to the entire universe using general relativity.

Answer 2

The car skids 135 m.

There is a three-fold increase in the speed of the car (150 / 50 = 3).

Thus, there must be a nine-fold increase in the stopping distance.