Unit 2 - Forces and Newton's Laws

Question 1

What is an external force

Answer 1

Force originating from outside of an object

Question 2

What is Newton’s first law

Answer 2

An object remains at rest or if in motion at a constant velocity unless acted on by a net external force

Question 3

Summarise Newton’s first law

Answer 3

No resultant force = no acceleration

Question 4

What is Newton’s second law

Answer 4

Acceleration is proportional to the net force and inversely proportional to the mass

Question 5

Equation from Newton’s second law

Answer 5

F = ma

Question 6

What is Newton’s second law

Answer 6

If object A exerts a force on object B then object B must exert a force of equal magnitude and opposite direction back on object A`

Question 7

What is weight

What is the equation for determining weight

Answer 7

The force of gravity

W = mg

Question 8

What is g

What can we approximate it to

Answer 8

9.81

10

Question 9

What is mass

Answer 9

The measure of inertia of an object

Question 10

_______ is constant but __________ changes due to differences in gravity

Answer 10

Mass

Weight

Question 11

What is a normal force

Answer 11

Force exerted by surfaces to prevent solid objects pushing through one another

Question 12

Forces PERPENDICULAR are

Answer 12

Normal

Question 13

Forces PARALLEL are

Answer 13

Frictional

Question 14

Give an instance where the normal force may not equal mg

Answer 14

When contact forces are not horizontal or there are extra vertical forces present

Question 15

When are frictional forces present

Answer 15

When two surfaces are sliding over one another

Question 16

Frictional forces are characterised by

Answer 16

The frictional coefficient

U

Question 17

What is the equation connecting frictional force and the normal force

Define the terms of this equation

Answer 17

Ff = u . Fn

Ff = frictional force 
u = frictional coefficient 
Fn = normal force

Question 18

What is static frictional force

Answer 18

Between a static object and the surface that it is resting on

Question 19

What equation must be used to determine the MAX force required to move an object

Define the terms of this equation

Answer 19

Fmax = u . Fn

Fmax -force required to move
u - frictional coefficient
Fn - normal force

Question 20

If you apply a force above Fmax what is seen

Answer 20

Kinetic frictional force will be exerted on it

Question 21

What is the equation for determining the kinetic frictional force

Answer 21

Fk = u . Fn

Where Fk = kinetic frictional force
u = friction coefficient
Fn = normal force

Question 22

Is there any static frictional force for a moving object

Answer 22

NO

Instead we would have kinetic frictional force

Question 23

For an object on an incline plane which is not moving what term would give the normal force

Answer 23

Mg cos theta = N

Question 24

Define tension

Answer 24

The force exerted by a rope/cable is the force of tension T

Question 25

Tension is only able to

Answer 25

Pull

Question 26

Steps for calculating tension in a system

Answer 26

1) draw forces acting on the object
2) write down F=ma for direction of tension
3) solve

Question 27

Cos 60 =

Answer 27

0.5