Physics End of Year Exam: Forces - Grade 9

Question 1

Force

Answer 1

is a push or pull or a turning effect, exerted by an object on another object (interaction)

Question 2

A vector

Answer 2

represented by an arrow
(see notes for diagram)

Question 3

Instrument for measurement

Answer 3

the newtonmeter/forcemeter/spring balance

Question 4

Base unit of force

Answer 4

In the SI is the newton (N)

Question 5

How big is a newton?

Answer 5

the typical force needed to:
- open a sode can = 20N
- flip a switch = 10N
- lift a bag = 200N

Question 6

Do we need a force to keep an object in motion?

Answer 6

Aristotle: “you need a force to keep an object in motion”
Newton: “If forces are balanced, the object will keep moving at a constant velocity”

Question 7

Newtons laws (the mathematical foundations of physics)

Answer 7

first law: when an object is at rest and no external force is applied on it, the object will stay at rest. when an object is moving and no external force is applied on it, the object will keep moving at a constant velocity.

Question 8

Magnetism

Answer 8

North and south attract
South and south repel
North and north repel

Question 9

Magnetism vs gravity

Answer 9

magnetism - only effects some metals
gravity - can only attract and effects everything
both - act at a distance

Question 10

4 fundamental forces in the universe

Answer 10

weakest to strongest
- gravity
- weak nuclear
- electromagnetic
- strong nuclear

Question 11

Equal force

Answer 11

same direction and magnitude

Question 12

Balanced force

Answer 12

same magnitude but opposite direction

Question 13

Mass and inertia

Answer 13

an object with a bigger mass will change its state of motion with greater difficulty than an object with a smaller mass

Question 14

Inertia (latin)

Answer 14

laziness, sluginess

Question 15

Newton’s second law of motion

Answer 15

F (force) = m (mass) x a (acceleration)

Question 16

The law of universal gravitation

Answer 16

F = G M(mass)xm/rsquared (distance)

Question 17

On earth

Answer 17

Weight (N) = 9.8 (ms -square) x mass (kg)

Question 18

Mass

Answer 18

is the amount of matter in an object
- it is measured with a balance
- the unit is the kilogram (kg)

Question 19

Weight

Answer 19

is the gravitational pull on an object
- is measured with a newtonmeter
- the unit is the newton (N)

Question 20

Newtons third law of motion

Answer 20

forces always come in pairs a.k.a. you can’t touch without being touched
to every action corresponds an equal but opposite reaction.
F/M = A, F/M = a