**Unit 2: Newton's Laws of
Motion**

**Problem Set B**

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 as the numerical value of g for situations upon Earth.
- Do not round any computed numbers until the last calculation.
- Unless told otherwise, enter your answers accurate to the second decimal place.
- Unless told otherwise, enter positive numbers for your answers.

**Problem 1:**

A small model rocket is launched vertically into the air. If the rocket has a mass of .19 kg and there is an upward thrust of 3.802 N, then what is the acceleration (in m/s/s) of the rocket?

**Problem 2:**

Claire deAisles applies a horizontal force to push a 78.6 kg supermarket crate at a constant speed of 1.2 m/s. If the coefficient of friction between the crate and the floor is .8, then determine the force (in Newtons) applied by Claire.

**Problem 3:**

A 9.7 kg bucket suspended by a rope accelerates upwards at a rate of 9.6 m/s/s. Determine the tension (in Newtons) in the rope which pulls on the string.

**Problem 4:**

What tension force (in Newtons) would allow a 1379.2 kg elevator to accelerate downwards (i.e., negative) at a rate of 4.8 m/s/s?

**Problem 5:**

Dexter Eius is walking through the cafeteria when he slips on some spilled milk and falls to the floor. Upon hitting the floor, he skids to a stop with an acceleration of -6.8 m/s/s. Dexter weighs 789.6 Newtons. Determine the coefficient of friction between Dexter and the floor. (Do not include a + or - sign on your answer; enter your answer, accurate to the fourth decimal place.)

**Problem 6:**

While decorating her apartment, Julie pushes a 2455.1-N dresser across the floor by applying a 3244.7-N horizontal force. If the coefficient of friction between the dresser and the floor is 0.728, then determine the acceleration (in m/s/s). (Enter your answer, accurate to the third decimal place.)

**Problem 7: **

Unbeknownst to most students, every time the school floors are waxed, the physics teachers get together to have a barrel of phun doing friction experiments in their socks (uhm - they have clothes on, its just that they don't have any shoes on their feet). On one occasion, Mr. Lewis applied a horizontal force to accelerate Mr. Smith (mass of 80 kg) rightward at a rate of 2.45 m/s/s. If the coefficient of friction between Mr. Smith's socks and the freshly waxed floors is 0.2, then with what force (in Newtons) must Mr. Lewis be pushing?

**Problem 8:**

A 1379.2 kg car skids to a stop across a road surface which has a coefficient of friction of 0.8 with respect to the tires. Determine the acceleration of the car in m/s/s. (Hint: Begin with a free-body diagram and work out the problem in terms of variables - m, g, mu, etc.)

**Problem 9: **

Claire deAisles applies a horizontal force of 1182.7 N to accelerate a 78.6 kg supermarket crate. The coefficient of friction between the crate and the floor is 0.80. Determine the acceleration (in m/s/s) of the crate. (Enter your answer, accurate to the third decimal place.)

**Problem 10:**

A 19.4 kg object moving rightward across a horizontal surface with a speed of 9.7 m/s The coefficient of friction between the object and the surface is 0.761. Determine the time (in seconds) required for the object to stop.

**Problem 11:**

A 24.4 N horizontal force is applied to a 0.075 kg hockey puck to accelerate it across the ice. Ignore friction and determine the final speed of the puck after being pushed for a time of .9 seconds.

**Problem 12:**

A 1186.1 kg car moving rightward with a speed of 34.6 m/s skids to a stop in 3.41 seconds. Determine the coefficient of friction between the car tires and the roadway. (Enter your answer, accurate to the third decimal place.)

**Problem 13:**

Claire deAisles applies a horizontal force of 1182.7 N to accelerate a 62.5-kg supermarket crate from a rest position. The coefficient of friction between the crate and the floor is 0.720. Determine the velocity of the crate after 1.9 seconds. (Enter your answer, accurate to the third decimal place.)

**Problem 14:**

A 4.15-kg bucket suspended by a rope is accelerated upwards from an initial rest position. If the tension in the rope is 98.2 Newtons, then determine the speed of the bucket after 3.8 seconds.

**Problem 15:**

Albert is attempting to drag his 68.6 kg Golden Retriever across the yard by applying a horizontal force. What force must be applied (in Newtons) to move the dog with a constant speed of 0.95 m/s? The coefficient of friction between the dog and the ground is 0.80.

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