1 Motion, forces and energy

Question 1

Common prefixes for units.

Answer 1

Prefix (symbol) Meaning
centi (c) ÷100
milli (m) ÷1000
kilo (k) ×1000
mega (M) ×1000000
giga (G) ×1000000000

Question 2

Scalar

Answer 2

Is a physical quantity that has magnitude but no direction
E.g.Speed, volume, mass

Question 3

Vector

Answer 3

Is a physical quantity that has both magnitude and direction.
E.g.Displacement, Velocity, acceleration, forces

Question 4

Resultant force

Answer 4

The effect or result

Question 5

Resolving Vectors

Answer 5

Shows the overall effect of the magnitude and direction of 2
or more vectors(Component vectors).

Question 6

How to calculate a resultant vector

Answer 6

Using the “head to tail method”
Add the vectors to get the distance
To get the R.F. use geometry or Pythagorean theorem.

Question 7

Speed

Answer 7

V = total distance travelled (m) ÷ total time taken (s)
Speed is a measurement of how far something travels in a unit of time.

Velocity is defined as speed in a given direction.

Question 8

Acceleration

Answer 8

=change in velocity (m/s) ÷ time taken (s)

Acceleration is the change in velocity per unit time

Question 9

Distance-time graphs

Answer 9

A straight, sloping line = constant speed
A straight, sloping line of higher gradient = faster constant speed
A flat/horizontal line = stationary (not moving).

Question 10

Speed-time graphs and gradient

Answer 10

A flat horizontal line at zero speed = stationary
A flat horizontal line above zero speed = constant speed
An upward sloping line = accelerating; the steeper the gradient, the higher the acceleration
A downward sloping line = decelerating.

Question 11

Gradient

Answer 11

increase in the y-axis ÷ increase in the x-axis

Question 12

Gravity

Answer 12

9.8 m/s*2

Question 12

Gravity

Answer 12

9.8 m/s*2

Question 13

Terminal velocity

Answer 13

The top speed reached by any object experiencing air resistance or a similar resistance force.

Question 14

Weight

Answer 14

Mass x gravity

Question 15

Mass

Answer 15

Volume x Density

Question 16

Density

Answer 16

Mass ÷ Volume

Question 17

Why do things float in water?

Answer 17

They have a lower density

Question 18

Force

Answer 18

Mass x acceleration

Question 19

Force due to gravity(fg) is the same as

Answer 19

Mass due to gravity(mg)

Question 20

Hooke’s law Is

Answer 20

Spring constant(K) = Force(F) ÷ Extension(x)
The force needed to stretch a spring or wire by one unit of length. Measured in N/m.

Question 21

Circular motion

Answer 21

Force(F)=Mass x Velocity*2
÷ radius

Question 22

Moment

Answer 22

Moment(T)= force x perpendicular distance to the pivot
A turning force.

Question 23

The principle of moment

Answer 23

A system will not rotate if the clockwise and anti-clockwise moments are equal.

Question 24

Centre of gravity

Answer 24

The imaginery point within an object that the mass and weight of the object is evenly dispersed around (also known as the centre of mass).

Question 25

Elastic collision

Answer 25

Kinetic energy and there fore momentum is fully conserved.

Question 26

Inelastic collision

Answer 26

Kinetic energy and there fore momentum is not conserved due to energy losses into other forms for example heat and sound.

Question 27

Momentum

Answer 27

Momentum(P)= Mass(m) x Velocity(V) Momentum is always conserved.

Question 28

Impulse

Answer 28

Change of momentum(impulse)= Force(F) x Time in the collision.

Question 29

What are the different types of energy stores 7

Answer 29

Kinetic Gravitational potential Thermal Electrostatic/magnetic Elastic potential Sound Chemical potential

Question 30

Energy

Answer 30

Is the ability to work

Question 31

What are the different types of energy transfers

Answer 31

Mechanical(force) Electrostatic Heating Electromagnetic, sound or other waves

Question 32

Conservation of energy

Answer 32

Energy cannot be eradicated or destroyed. It can only be transformed from one state to the other. Ek=Ep

Question 33

Sankey diagram

Answer 33

Used to show energy transfers while also giving an indication of how much energy is transferred at each step.

Question 34

Kinetic energy

Answer 34

1/2×mass (kg) × [velocity (m/s)]*2 The energy of moving objects.

Question 35

Gravitational potential

Answer 35

mass (kg) × acceleration of gravity (m/s*2) × change in height (m) Energy is stored when an object is raised to a height with in a gravitational field.

Question 36

Work

Answer 36

W=Force x Distance work done=energy transferred

Question 37

Power

Answer 37

Power = Work ÷ Time The rate at which work is done, or rate of energy transfer.

Question 38

Boiler

Answer 38

Uses heat from the burning of fuels to boil water into steam.

Question 39

Turbine

Answer 39

Transforms thermal energy from a fluid(liquid or gas) into rotated kinetic energy.

Question 40

Generator

Answer 40

Consists of a coil/s of wire that rotate in a magnetic field to produce an electrical current.

Question 41

Energy resources

Answer 41

Fossil fuels (coal, oil, gas) Nuclear Hydroelectric Tidal Wave Solar Wind Geothermal

Question 42

Energy efficiency

Answer 42

Efficiency(%)= (Useful energy÷Total energy) x 100 No energy transfer is 100% efficient.

Question 43

Pressure

Answer 43

Pressure= Force ÷ Area Pressure is a measure of force per area

Question 44

Pressure in liquids

Answer 44

Pressure= Change in height X density(Pa) x gravitational field strength.

Question 45

Conditions needed for equilibrium

Answer 45

No Resultant force No Resultant moment

Question 46

Air resistance

Answer 46

Consider a ball falling. Gravity pulls the ball downwards, but as the ball goes faster, air resistance acts upwards

Question 47

KWH

Answer 47

energy transferred in one hour at a rate of transfer of 1 kW