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

**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 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.

**Multiple Choice:**

Which of the following statements are true? Choose all that apply by listing their letter in alphabetical order with no spaces, commas, or other marks between letters.

a. If the net force acting upon an object is directed to the right, then the object MUST be moving to the right.

b. The weight of an object can be determined by multiplying the mass of the object (in kilograms) by the force of gravity (in Newtons).

c. If an object is moving upwards, then there MUST be an upward force acting upon the object.

d. The mass of an object on Earth will be the same as the mass of the same object when placed on the moon.

e. A downward moving elevator, supported by a cable, is slowing down. In this instance, the upward force of tension MUST be greater than the downward force of gravity.

f. The weight of an object is the same thing as the force of gravity acting upon an object.

g. If an object is moving to the right and slowing down, then one can be certain that either there is more right force than left force acting upon the object or that there is no left force acting upon the object.

h. If a falling object has reached a terminal velocity, then it must be encountering air resistance.

i. If an object is moving to the right and slowing down, then one can be certain that either there is more left force than right force acting upon the object or that there is no right force acting upon the object.

j. If an object is accelerating upwards, then there MUST be an upward force acting upon the object.

(List all in alphabetical order with no spaces or punctuation marks.)

**Problem 1:**

If an object weighs 579 Newtons on Earth, then its mass is ____ kg.

**Problem 2:**

Determine the weight (in Newtons) of a 95.9-kg object on planet Earth.

**Problem 3:**

The acceleration of gravity on planet X is 19.2 m/s/s. If an object weighs 766 Newtons on Earth, then its mass on planet X would be ____ kg.

**Problem 4:**

Consider the free-body diagram at the right. Determine the acceleration (in m/s/s) of the object. Given: F F F |

**Problem 5:**

Consider the free-body diagram at the right. Determine the acceleration (in m/s/s) of the object. Given: F F F |

**Problem 6:**

A 9.43-kg bucket suspended by a rope accelerates upwards at a rate of 4.74 m/s/s. Determine the tension (in Newtons) in the rope which pulls on the string.

**Problem 7:**

A 4.89-kg bucket suspended by a rope is accelerated upwards. If the tension in the rope is 96.7 Newtons, then determine the acceleration (in m/s/s) of the bucket.

**Problem 8:**

A 4.89-kg bucket suspended by a rope is moving upwards with a constant velocity of 5.7 m/s. Determine the tension (in Newtons) in the rope.

**Problem 9:**

A 71.9-Newton rightward force is applied to a 9.85-kg crate to accelerate it from rest across a horizontal surface. If the crate experiences a friction force of 53.5 Newtons, then determine the acceleration (in m/s/s). Enter a - value for a leftward acceleration.

**Problem 10:**

What applied force (in Newtons) would be required to give a 19.22-kg object an acceleration of 2.41 m/s/s if the force of friction opposing it is 87.5 Newtons?

**Problem 11:**

A 8.73-kg object experiences a rightward acceleration of 3.86 m/s/s when a 106.2-N rightward force is exerted upon it. Determine the magnitude of the force of friction (in Newtons) which opposes this object's motion.

**Problem 12:**

(Referring to the previous problem.) Determine the coefficient of friction between the object and the surface over which it is pulled. Enter a positive value which is accurate to the third decimal place.

**Problem 13:**

Chuck Wagon applies a horizontal force of 790 N to accelerate a 65.2-kg box from a rest position. The coefficient of friction between the crate and the floor is 0.938. Determine the acceleration (in m/s/s) of the crate. Enter your answer, accurate to the third decimal place.

**Problem 14:**

Chuck Wagon applies a horizontal force of 394 N to accelerate a 44.2-kg box from a rest position. The coefficient of friction between the crate and the floor is 0.873. Determine the acceleration (in m/s/s) of the crate. Enter your answer, accurate to the third decimal place.

**Problem 15:**

A 68.2-kg falling skydiver is encountering 389 N of air resistance at a given moment during her fall. Determine the accceleration (in m/s/s) of the skydiver. If downward, then enter a negative answer.

**Problem 16:**

A 68.2-kg falling skydiver is encountering 832 N of air resistance at a given moment during her fall. Determine the accceleration (in m/s/s) of the skydiver. If downward, then enter a negative answer.

**Problem 17:**

A 628-Newton force is applied to a 704-Newton object to slide it across a rough surface having a coefficient of friction of .482. Determine the acceleration (in m/s/s) of the object.

**Problem 18:**

A 7.78-kg object experiences a rightward acceleration of 4.45 m/s/s when a 51.2-Newton rightward force is applied to it. Determine the coefficient of friction between the surface and the object. Enter your answer accurate to the third decimal place.

**Problem 19:**

A 1378-kg car is skidding to a stop along a horizontal surface. The car decelerates from 34.2 m/s to a rest position in 3.99 seconds. Assuming negligible air resistance, determine the coefficient of friction between the car tires and the road surface. Enter a positive value that is accurate to the third decimal place. (If necessary, review the definition of and the equation for computing the acceleration.)

**Problem 20:**

Determine the amount of force (in Newtons) which must be applied to a 21.5-kg object to drag it to the right at a constant speed of 3.41 m/s. The coefficient of friction between the surface and the object is 0.678.

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