P5 Contact and Non-Contact Forces (page 201)

Question 1

What is a Force?

Answer 1

Frce is a vector quantity

Question 2

Vector quantities have what?

Answer 2

a magnitude and a direction.

Question 3

Lofs of physical quantities are vector quantities, give examples?

Answer 3

Vector quantities:

force, velocity, displacement, acceleration, momentum, etc.

Question 4

Some physical quantities only have what? and what are these called?

Answer 4

only have magnitude and no direction.

They are called scalar quantties.

Question 5

Give examples of Scalar quantities?

Answer 5

speed, distance, mass, temperature, time etc.

Question 6

How are Vectors usually represented by? explain why?

Answer 6

An arrow - the length of the arrow shows the magnitude, and the direction of the arrow shows the direction of the quantity.

Question 7

Veloity is a what quantity?

Answer 7

Vector

Question 8

speed is a what quantity?

Answer 8

scalar quantity

Question 9

Look at diagram 2 on page 201, Both bikes are travelling at the same speed v. (the length of each arrow is the same).

Why do they have different velocities?

Answer 9

because they are travelling in different directions.

Question 10

Can forces be contact or non-contact, or both?

Answer 10

both.

Question 11

A force is a push or a pull on an object that is caused by what?

Answer 11

by it interacting with something.

(all forces are either contact or non-contact forces).

Question 12

When two objects have to be touching for a force to act, what is that force called?

Answer 12

a contact force.

Question 13

give examples of contact force?

Answer 13

e.g. friction, air resistance, tension in ropes, normal contact force, etc

Question 14

If the objects do not need to be touching for the corce to act, what is the force called?

Answer 14

the force is a non-contact force.

Question 15

Give examples of non-contact force?

Answer 15

e.g. magnetic force, gravatational force, electrostatic force, etc.

Question 16

When two objects interact, what do this mean?

Answer 16

there is a force produced on both objects.

Question 17

What is an interaction pair?

Answer 17

it is a pair of forces that are equal and opposite and act on two interacting objects. (This is basically Newton’s Third Law - see page 212).

Question 18

The Sun and the Earth are attracted to each other by what force? explain why?

Answer 18

by the gravitational force.

This is a non-contact force. An equal but opposite force of the attraction is felt by both the Sun and the Earth

(the sun is attracted to the Earth, and the Earth is attracted to the Sun).

Question 19

A chair exerts a force on the ground, whilst the ground pushes back at the chair with the same force (the normal contact force) explain what this means?

Answer 19

Equal but opposite forces are felt by both the chair and the ground.

(the chair pushes on the ground, and the ground pushes on the chair).

Question 20

A tennis ball is dropped from a height. Name one contact force and one non-contact force that act on the ball as it falls. (2 marks)

Answer 20

Contact force: air resistance (1 mark)
Non-contact force: gravitational force (1 mark)

Question 21

Name two examples of:

a) a scalar quantity
b) a vector quantity

(4 marks)

Answer 21

Any two from: e.g speed/distance/mass/temperature (2 marks)