Forces

Question 1

What is a vector?

Answer 1

Has magnitude and direction.

Question 2

What is a scalar?

Answer 2

A physical quantity that has magnitude.

Question 3

Examples of scalars

Answer 3

Distance 
Speed
Time
Energy
Mass

Question 4

Examples of vectors

Answer 4

Displacement
Velocity
Acceleration
Force

Question 5

What do forces make an object do?

Answer 5

Start moving 
Stop moving
Change speed
Change direction 
Change shape

Question 6

What are the contact forces?

Answer 6

Friction
Air resistance
Reaction
Tension

Question 7

What are the none contact forces?

Answer 7

Gravitational force
Magnetic forces
Electrostatic forces

Question 8

What is weight?

Answer 8

The weight of an object is the force acting on it due to gravity. Weight is measured in Newtons (N).

Question 9

What is mass?

Answer 9

The mass of an object depends on the quantity of matter in it. Mass is measured in kilograms (Kg).

Question 10

What is the equation for weight?

Answer 10

Weight = mass x gravitational field strength

W= m x g

Question 11

What is terminal velocity?

Answer 11

Terminal velocity is when the object reaches a constant velocity when the frictional force in it is equal and opposite to its weight. The resultant force is then 0 so the acceleration is 0.

Question 12

What is the resultant force of an object released in fluid?

Answer 12

The weight - frictional force

Question 13

What is the centre of mass of an object?

Answer 13

The centre of mass of an object is the point at which it’s mass can be thought of as being concentrated.

Question 14

What two factors affect the stability of an object?

Answer 14

The width of the base of an object

The height of its centre of mass- higher centre of mass = less stable

Question 15

How do you work out the centre of mass of an irregular shape?

Answer 15

Cut out irregular shape
Put hole in corner
Use clamp stand to suspend it and draw vertical line using plumb line
Repeat hanging the shape from different corners
Where all lines meet is the centre of mass.

Question 16

What are forces in an interaction pair?

Answer 16

They are equal in size and opposite in direction.

Question 17

What is the resultant force when an object is balanced?

Answer 17

Resultant force= 0

Question 18

What happens when forces are imbalanced?

Answer 18

The object can change speed direction or shape.

Question 19

What is work done?

Answer 19

Work is the amount of energy transferred to move a certain distance

Question 20

What is the equation for work done?

Answer 20

Work done= force x distance

Question 21

What is Hooke’s law?

Answer 21

The extension of a spring is directly proportional to the force applied as long as the limit of proportionality isn’t exceeded.

Question 22

What is the equation for force applied?

Answer 22

Force applied= spring constant x extension

F= k x e

Question 23

Parallelogram of forces

Answer 23

Need a scale
Draw parallelogram using angles and lengths (see book)
Find the length of the dotted line

Question 24

Average speeds

Answer 24

Person walking: 1.5
Person cycling: 6
Person running: 3 
Wind on windy day: 18 
Car in motorway: 31 
Car in built up area: 13
Sound in air:330 

• all in m/s

Speeds are rarely constant, called ununiform

Question 25

What is speed?

Answer 25

Speed is a scalar. It is how fast you are travelling

Question 26

What is velocity?

Answer 26

Velocity is a vector. It is speed in a given direction

Question 27

What is acceleration?

Answer 27

Acceleration is the change in speed or velocity over time. If negative it is called deceleration.

Question 28

What is the equation for acceleration?

Answer 28

A= change in velocity/ time taken

Question 29

How do you find distance on a velocity time graph?

Answer 29

Area under the graph

Question 30

What is the equation for a constantly accelerating body?

Answer 30

V^2 = u^2 + 2as Final velocity = initial velocity + (2 x acceleration x displacement)

Question 31

What is Newton’s 1st law?

Answer 31

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted on by an imbalanced force The tendency of an object to stay at rest or move in uniform motion is called inertia. The inertia of an object depends on its mass.

Question 32

What is Newton’s 2nd law?

Answer 32

The acceleration of an object is proportional to the resultant force of an object and inversely proportional to the mass of an object.

Question 33

What is Newton’s 3rd law?

Answer 33

For every action there is an equal and opposite action. Forces which are in equilibrium are equal and opposite.

Question 34

What is the equation for force?

Answer 34

Force = mass x acceleration

Question 35

Factors effecting top speed

Answer 35

``` Surface of road Car weight Friction Air resistance/ aerodynamics/ stream lining Acceleration Power of engine ```

Question 36

How do you find stopping distance?

Answer 36

Stopping distance= thinking distance + braking distance

Question 37

Factors effecting thinking distance

Answer 37

Tiredness Drugs Alcohol Distractions (people phone music)

Question 38

Factors effecting braking distance

Answer 38

``` Surface of road Quality of brakes Quality of tyres Weight of car Speed of car Weather Gradient of the road ```

Question 39

What is the equation for momentum?

Answer 39

Momentum= mass x velocity Momentum is measured in kg m/s

Question 40

What is momentum affected by?

Answer 40

Mass: larger mass= larger momentum Velocity: the faster the object moves the larger the momentum

Question 41

What happens to momentum when no external forces act?

Answer 41

Momentum is conserved Momentum before= momentum after

Question 42

How to work out velocity after a collision

Answer 42

Work out momentum of each object Work out overall combined momentum Work out combined mass Calculate final velocity using momentum equation