ITP HOMEWORK

Ch. 2

Mechanical Equilibrium

Pg. 24 (1,2,4,7,8,12,14)

ITP HOMEWORK

Ch. 2Mechanical EquilibriumPg. 24 (3,5,9,10,15,16,22,23)

ITP HOMEWORK

Ch. 2.1-2.4

Mechanical Equilibrium

Pg. 24 (1-4, 7-10, 14-16)

1. What is the difference between force and net force on an object.

1. What is the difference between force and net force on an object.

Force is a push or a pull; net force is the combination of all forces acting on an object.

2. What is the net force on a box that is being pulled to the right w/ 40 N and to the left with 30 N?

30 N 40 N

2. What is the net force on a box that is being pulled to the right w/ 40 N and to the left with 30 N?

10 N to the right

30 N 40 N

3. What name is given to the stretching force that occurs in a spring or rope being pulled?

Spring force and Tension

4. What two quantities are necessary to determine a vector quantity?

Magnitude and direction

7. How much tension is in a rope that holds up a 20-N bag of apples at rest?

Since the bag is at rest, it is in mechanical equilibrium. Therefore, there must be 20N of tension force to balance the 20N of weight force due to gravity.

This is referred to in the book as static equilibrium.

8. What does F = 0 mean?

The sum of all forces acting on a body are balanced (or net force is equal to zero)

9. What is the net force on an object at rest?

9. What is the net force on an object at rest?

Zero. All forces are balanced.

10. When you do pull-ups and you hang at rest, how much of your weight is supported by each arm?

10. When you do pull-ups and you hang at rest, how much of your weight is supported by each arm?

Each arm supports one-half of your weight.

14. Can an object be moving and still be in (mechanical) equilibrium?

14. Can an object be moving and still be in (mechanical) equilibrium?

Yes. If the object moves at a constant speed in a straight line, then the net force on the object is equal to zero.

This is referred to in the book as dynamic equilibrium.

15. If you pull a crate across a factory floor at a constant speed in a constant direction, what is the size of the force of friction on the crate compared with your pull if your pull force is 50 N? What is the net force? Is it in mechanical equilibrium? If so, which type?

50 N of pull force

Box is moving at a constant speed and direction to the left.

???? of friction force

15. If you pull a crate across a factory floor at a constant speed in a constant direction, what is the size of the force of friction on the crate compared with your pull if your pull force is 50 N? What is the net force? Is it in mechanical equilibrium? If so, which type?

Both the pull force and the friction force are equal in magnitude, but are in opposite directions. Thus, the net force is zero and the object is in dynamic equilibrium.

50 N of pull force

Box is moving at a constant speed and direction to the left

(Dynamic equilibrium)

50 N of friction force

16. Distinguish between static equilibrium and dynamic equilibrium.

An object at rest is said to be in static equilibrium.

An object moving in a straight line at a constant speed is said to be in dynamic equilibrium.

For each case, the net force = 0, thus the forces acting are balanced.

22. and 23.

22. B is the same as D, then C and then A. 23. C, then D, then A is the same as B.

5. How does a vector quantity differ from a scalar quantity?

Vector quantities show magnitude and direction and scalar quantities show only magnitude.

12. What two forces compress a spring inside a weighing scale when you weight yourself?

Your weight (your mass accelerated by gravity) and the support force of the floor (pushing upward).