1. Motion, forces and energy

Question 1

Speed formula

Answer 1

average speed (m/s) = total distance travelled (m) / total time taken (s)

Question 2

What is speed?

Answer 2

Speed is the distance covered per (time unit)

Question 3

What is speed normally measured in?

Answer 3

Meters per second (m/s)

Question 4

Acceleration Formula

Answer 4

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

Question 5

What is acceleration?

Answer 5

The increase in speed of an object

Question 6

What is acceleration measured in?

Answer 6

Meters per second squared (m/s^2)

Question 7

What is the value of gravity on earth?

Answer 7

9.8 m/s^2

Question 8

Weight definition

Answer 8

The gravitational force acting on an object that has mass.

Question 9

What are forces measured in?

Answer 9

Newtons (N)

Question 10

Gravitational field strength equation

Answer 10

gravitational field strength (N/kg)g = weight (N) / mass (kg)

Question 11

Density equation

Answer 11

density (kg/m3) = mass (kg) / volume(m3)

Question 12

Density definition

Answer 12

How much mass there is per unit volume

Question 13

What is density measured in?

Answer 13

kg/m^3 or g/cm^3.

Question 14

How do you measure the density of a regular object?

Answer 14

By measuring its mass on a scale and finding its volume from its dimensions

Question 15

How do you measure the density of an irregular object?

Answer 15

By measuring its mass and then finding its volume using the water displacement method

Question 16

Why will some objects float?

Answer 16

If the density of the object is less than the density of water, it will float.

Question 17

Why do some objects sink?

Answer 17

If an object has a density greater than water, then the object will sink in water.

Question 18

Why does oil float on water?

Answer 18

Oil floats on water because its density is less than 1  g/cm^3.

Question 19

How do forces affect objects?

Answer 19

They can:
- change their shape
- change their size
- change their velocity
- change their direction of motion.

Question 20

Air resistance definition

Answer 20

A force of friction between the air and the object moving through it

Question 21

What happens if the forces acting on an object are unbalanced?

Answer 21

There is a resultant force and therefore, a change in speed

Question 22

What happens if the forces acting on an object are balanced?

Answer 22

There is no resultant force and therefore, the speed of the object doesn’t change

Question 23

Force equation

Answer 23

force (N) =mass (kg) × acceleration (m/s^2)

Question 24

For an object moving in a circular path, more force is needed if:

Answer 24

• the mass of the object increases
• the speed of the object increases
• the radius of the circle decreases.

Question 25

Spring constant equation

Answer 25

Spring constant (N/m) = Force (N) / extension (m)

Question 26

Hooke’s Law

Answer 26

The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

Question 27

What changes the size of a moment?

Answer 27

The turning force depends on the size of the force and the distance of the force from the pivot

Question 28

Moment equation

Answer 28

Moment (Nm) = force (N) × perpendicular distance to the pivot (m)

Question 29

How is the distance measured for a moment equation?

Answer 29

The distance is measured at right angles to the direction of the force being applied

Question 30

How do you find the direction an object will rotate?

Answer 30

Add up the moments, not the forces, and find out which way the object will rotate.

Question 31

What distance you measure to calculate the force of a moment?

Answer 31

The distance between the pivot and the point where the force is applied, is where it is measured.

Question 32

The principle of moments

Answer 32

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

Question 33

How to find multiple turning points

Answer 33

Add together all the clockwise moments to find the total clockwise moment and then do the same for the anticlockwise moments.

Question 34

Friction definition

Answer 34

Friction is the force between two surfaces that oppose the motion and produces heating.

Question 35

Drag definition

Answer 35

Drag is the frictional force acting on an object moving through a liquid

Question 36

Momentum definition

Answer 36

The quantity of motion of a moving body, measured as a product of its mass and velocity

Question 37

Momentum equation

Answer 37

momentum (kg m/s) = mass (kg)×velocity (m/s)

Question 38

The law of conservation of momentum

Answer 38

In any collision, the total momentum before and after the collision is the same

Question 39

Impulse definition

Answer 39

Change in momentum

Question 40

Impulse equation

Answer 40

Force x change in time

Question 41

Resultant force

Answer 41

change in momentum per unit

Question 42

The principle of conservation of energy

Answer 42

Energy cannot be created or destroyed, only converted from one store to another

Question 43

Kinetic energy

Answer 43

Ek =1/2mv^2

Question 44

Gravitational Potential

Answer 44

ΔEp = mgΔh

Question 45

What can energy be stored as?

Answer 45

kinetic, gravitational potential, chemical, elastic (strain), nuclear, electrostatic and internal (thermal)

Question 46

What is efficiency?

Answer 46

(%) efficiency = (useful energy output)/(total energy input) (×100%)

Question 47

Pressure equation

Answer 47

pressure = Force/Area

Question 48

Equation for the change in pressure beneath the surface of a liquid

Answer 48

Δp=ρgΔh