TEST 8 SCIENCES

Monday, February 16

8th A y B

Study Guide

ANSWER:

1. What is gravitational force (gravity)?

2. What is weight?

3. What is mass? how do they differ (mass and weight)?

4. Describe the first two laws of Isaac Newton that describe motion and its related forces.

5. Describe the Gravitational Theory.

6. What is Friction (frictional force)? List 3 examples of friction (name the surfaces involved)

7. List three ways we can reduce friction.

8. List three harms of friction.

9. What is inertia?

10. Relationship between inertia and mass.

T or F

1. A large mass exerts a stronger pull than does a smaller mass at the same distance. True (gravitational attraction depends on their masses and the distance between them (objects)).

2. Objects with different masses accelerate downward at the same rate. True. (more force is needed to accelerate a larger mass, and because of its greater mass, the pull of gravity acting on the larger mass is greater than the pull of gravity acting on the small mass).

3. Acceleration and force are directly proportional, as force increases, acceleration increases. True.

4. Inertia is not a force, is a quality of an object that causes it to resist any change in its state of rest or motion. True.

5. Friction occurs when surfaces rub against each other. True.

6. Friction is greater when motion is starting than when it is continuing. True.

7. Friction is greater for heavier weight. True.

8. The greater the mass, the greater the inertia, that is the greater the tendency of an object to remain as it is and the greater the force needed to alter the object's state. True

Practice

1. Find the Force (weight) of an object if its mass is 220 Lbs.

2. Find the acceleration of a 75 kg skater that pushes off from a wall with a force of 200 N.

3. Fin the mass of an object with a force of 15 N.

4. Find the weight of your parents and siblings on Earth.

5. Find the weight of your parents and siblings on Mars and Moon.