Question

chapter 12 forces and motion
section 12.1 forces (pages 356–362)
this section describes what forces are and explains how forces affect the motion of various objects.
reading strategy (page 356)
relating text and visuals as you read about forces, look carefully at figures 2, 3, and 5 in your textbook. then complete the table by describing the forces and motion shown in each figure. for more information on this reading strategy, see the reading and study skills in the skills and reference handbook at the end of your textbook.
forces and motion

figure	is net force 0?	effect on motion
2b
3
5a
5b

what is a force? (pages 356–357)

1. a force is defined as a(n) or a(n) that acts on an object.
2. is the following sentence true or false? a force can act to cause an object at rest to move or it can accelerate an object that is already moving.
3. how can a force change the motion of an object that is already moving?
4. circle the letter of the best answer. what force causes a 1 - kg mass to accelerate at a rate of 1 meter per second each second?

a. 1 kg/m•s² b. 1 kg/s
c. 1 kg•m d. 1 newton
combining forces (pages 357–358)

1. the overall force acting on an object after all the forces are combined is the
2. how do balanced and unbalanced forces affect the motion of an object?

Explanation:

Step1: Define force

A force is a push or a pull that acts on an object.

Step2: Analyze effect of force on motion

A force can cause an object at rest to move or accelerate a moving object. It can change the speed or direction of a moving object.

Step3: Recall Newton's second - law for force unit

According to Newton's second - law \(F = ma\), when \(m = 1\mathrm{kg}\) and \(a=1\mathrm{m/s}^2\), \(F = 1\mathrm{kg}\times1\mathrm{m/s}^2=1\mathrm{N}\). The unit of force is newton.

Step4: Define net force

The overall force acting on an object after all forces are combined is the net force.

Step5: Analyze balanced and unbalanced forces

Balanced forces result in no change in motion (object remains at rest or moves with constant velocity). Unbalanced forces cause a change in the object's motion (acceleration).

Answer:

1. push; pull
2. True
3. It can change the speed or direction of the object.
4. d. 1 newton
5. net force
6. Balanced forces: no change in motion (object at rest stays at rest or object in motion moves with constant velocity). Unbalanced forces: cause a change in the object's motion (acceleration).