**Unit 5: Work, Energy and
Power**

**Problem Set C**

The following selection of problems are sample problems. Individual student problem sets will vary since numerical information is randomly-generated.

**Directions:**

For the following problems:

- Compute the unknown quantity and enter the answer in the blank.
- Use 9.8 m/s/s for the numerical value of g for situations upon Earth
- Do not round any computed numbers until the last calculation.
- Enter your answers accurate to the second decimal place (unless told otherwise).

**Problem 1: **

A car is moving across a level highway with a speed of 32.1 m/s. The brakes are applied and the wheels become locked as the 1124-kg car skids to a stop. The braking distance is 122.4 meters. Determine the braking force (in Newtons) acting upon the car.

**Problem 2: **

Suzie Lavtaski is at rest on top of a ski slope with an initial height of 1687.4 meters above the slope's bottom. While descending the hill, a total amount of work of - 264987 Joules are done upon her 64-kg body. Determine her speed (in m/s) at the bottom of the hill just prior to skidding to a stop.

**Problem 3: **

A 0.728-kg volleyball approaches a GBS spiker with a speed of 2.62 m/s and a height of 1.9 m. The player does +28.1 Joules of work upon the ball during the spiking process. Determine the speed (in m/s) of the ball just prior to hitting the ground.

**Problem 4: **

A 231-gram baseball leaves the bat with a speed of 76.2 m/s. It sails through the air, encountering air resistance which does a total of -236 Joules of work on the ball over the course of its entire trajectory. What is its speed (in m/s) of the ball the instant prior to being caught (at the same height as which it was hit)?

**Problem 5: **

A bowling ball is attached to a 2.3-meter long cable and hung from the ceiling. The cable is kept taut and the ball is raised to an initial height of 1.64 meters above the classroom floor. It is released from rest and allowed to swing as a pendulum. Determine its speed (in m/s) when it is at a height of .76 meters above the floor.

**Problem 6: **

Pete Zaria applies a rightward force of 5.43 Newtons over a distance of .92 meters to set a 843 gram root beer mug from rest into motion along a level countertop which is 0.62-meters above the parlor floor. Determine the speed of the mug after Pete is done pushing it. (Assume negligible friction forces.) Enter your answer accurate to the third decimal place.

**Problem 7: **

Esteemed Chinese ski jumper, Li Ping Phar, leaves the jump ramp with an initial speed of 33.1 m/s and a height (relative to the bottom of the ski hill) of 56.2 meters. She encounters -7624 Joules of work due to air resistance during her flight through the air. Determine the speed (in m/s) of her 45.2-kg body the instant prior to striking the ground at the bottom of the hill.

**Problem 8: **

A 0.276-kg baseball is moving horizontally with a speed of 42.1 m/s when it is caught by the catcher. The catcher's mitt recoils horizontally a distance of 31.2 cm before the ball is brought is stopped. Determine the force (in Newtons) which is applied by the catcher to the ball.

**Problem 9: **

A physics teacher does 36.2 Joules of work on a 2.81-kg pile of snow to both lift it off the ground and to set it into motion. The pile of snow leaves the shovel with a speed of 2.1 m/s. What is the height (in m) of the snow when it leaves the shovel? Enter your answer accurate to the third decimal place.

**Problem 10: **

A 843-kg roller coaster car is lifted to a height of 57.1 meters above the ground where it begins its descent from an initial rest position. A total of -14061 Joules of work are done on the car by air resistance as it descends the first hill and rises to the top of the first loop - a height of 16.2 m. What is its speed (in m/s) at the top of this loop?

**Problem 11: **

A 3.62 kg physics cart starts from rest at the top of a .762-meter high incline. Determine the speed (in m/s) of the cart after it has rolled to a height of .181 meters. (Neglect the effect of friction forces.) Enter your answer accurate to the third decimal place.

**Problem 12: **

A 47.1 gram Hot wheels car is moving along the ground with a speed of 3.62 m/s. It approaches a hill inclined at 23.1 degrees to the horizontal. It rolls up the hill and then back down. To what height (in meters) will the car roll up the incline? (Ignore any effects of rotation and friction.) Enter your answer accurate to the third decimal place.

**Problem 13: **

A 188-gram ball is thrown straight upwards with an initial speed of 33.1 m/s. To what height (in meters) will it rise if the amount of air resistance which it encounters is negligible?

**Problem 14: **

A 562-kg roller coaster car is moving with a speed of 19 m/s at the very end of the ShockWave roller coaster track. A hydraulic braking system applies a 11437-Newton force at the loading dock to slow the car to a speed of 2.6 m/s. Over what horizontal distance (in meters) is the force applied?

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