Physics Ch 3.1 Pushes and Pulls

Question 1

What causes motion? What is the definition of that answer?

Answer 1

Forces cause motion. A force is that which changes or tends to change an objects state of rest or uniform motíon in a straight line.

Question 2

What are the characteristic effects of forces

Answer 2

(1) Forces can change the shape or size of an object
(2) Forces can alter the speed of an object. That is, it can make things go faster or slower
(3) Forces can change the direction of moving objects

Question 3

What are the types of forces?

Answer 3

NON - CONTACT
- gravity, magnetic, electromagnetic
CONTACT
- friction, tension

Question 4

Explain gravity.

Answer 4

This is a type of non contact force. It is the force which pulls us towards the centre of the Earth.
Weight is the pull of gravity acting on an object. Weight changes as gravity changes.

Question 4

Explain non contact forces

Answer 4

These forces can act over large surfaces of air or empty space without two objects touching.

Question 5

What is the difference between the gravity on the moon and earth?

Answer 5

The moon has less gravity than that of Earth’s gravity. The moon’s gravity is 1/6th than that of Earth’s gravity. An astronaut will weigh six times more on Earth than on the moon.

Question 6

What is “weightless”?

Answer 6

Weightless mean there is no pull of gravity

Question 7

(go through lab copy and test for the sums on weight - sums are the rest of the chapter)
(also go through lab copy to see all notes again)

Question 8

NON CONTACT FORCES
- MAGNETIC FORCE
A magnet has two poles - North Pole and South Pole
Opposite poles attract. Similar poles repel

Question 9

ELECTROSTATIC FORCE:
The electrostatic force gives rise to static electric charges

Question 10

CONTACT FORCES-
Contact forces arise when two objects are in contact with each other.

Question 11

FRICTION:
Friction is a contact force that slows down moving objects.
Force always acts opposite to the direction of motion.

Question 12

What are the positive and negative effects of friction?

Answer 12

Negative Factors:
(1) When we want things to move, friction is a nuisance.
(2) Friction causes wear and tear of moving parts in machines, moving parts, motors, etc.

Positive Factors:
(1) When we want things to stop, friction is helpful.
(2) The friction on our shoes and the ground prevent us from slipping.
(3) Without friction, we wouldn’t be able to walk, write or even hold a pencil. Friction is used in brake pads in cars to slow down.

Question 13

How do we minimise/reduce friction

Answer 13

1. By using highly polished surfaces
2. Using lubricant, such as oil, wax, or grease.

Question 14

CONTACT FORCES -
TENSION

Answer 14

This force occurs when two objects pull each other through a material medium (see copy for diagram reference).
–> The weight of the object pulls the string downwards. The string pulls it upwards with an equal upward force called tension.

Question 15

An instrument for measuring forces is called a Newton Meter or Spring Balance.

Question 16

HOOKES LAW (v. imp.) (word for word definition)

Answer 16

When an elastic object (spring) is stretched to the stretching force is proportional to the extension of the object, provided the force is not so not so great that it deforms the object permanently.

Question 17

Forces always occur in equal and opposite pairs called action and reaction.