P2 Spaced Learning

All you need to do is remember the red highlighted words!

P2 Spaced Learning

All you need to do is remember the red highlighted words!

P2 Topic 4

Momentum, energy, work &

power

Brakes have been applied and car is slowing. Affected by:1. Road conditions (icy or wet)Note: this affects the friction between the road and tyre.2. Brakes are worn3. Speed of car4. The mass of the car

Driver is thinking/reacting before deciding to apply the brakes. Affected by:1. Drugs (alcohol/illegal)2. Tired3. Distracted (mobile etc)Or anything that slows your time to react.

STOPPING DISTANCE

Energy Transferred means the same thing as Work Done;Energy transferred = Work DoneBoth are measured in joules (J)

There are different kinds of energy that cannot be destroyed or created, they can however be transferred

from on type to another. A battery for example transfers chemical energy to electrical energy

Most Kids Hate Learning G C S E Energy Namesagnetic

inetic

eat ight

ravitational

hemical

ound

lectrical

lastic

uclear

Energy transferred = Work Doneis calculated;

Work Done (J) = Applied Force (N) x distance moved (m) (in direction of force)

W = F x d

W = F x dW = 500 x 2W = 100J

NB: 1kg = 10N

Gravitational Potential Energy (GPE) is energy an object has because of its height in a gravitational field.

Kinetic Energy (KE) is energy an object has because it is moving.

Remembering that energy cannot be destroyed or created, they can however be transferred gives us an easy example to see these energies at work. If a cannon ball is falls from 5m it converts GPE to KE as it falls and in this case then to sound!

GPE = m x g x h

KE = ½ m x v2

Mass (kg) (J, Joules)

Gravitational Field Strength (N/kg)

Vertical height change (m)

Velocity2 (m/s2)

Make sure that you can remember the units!!!Also if an object has zero height or speed in must have zero

GPE or KE accordingly and the energy must have all transferred somewhere!!

Power is a measure of how fast you can do work or how fast energy is transferred.

Take these two cars they both have a 1.6 litre turbo engine and the same chemical energy power source (petrol). The one on the right uses 1 litre of fuel for

every 325m where as the one on the left uses 1 litre of fuel for every 18150m.

𝑃𝑜𝑤𝑒𝑟 (𝑊𝑎𝑡𝑡𝑠 ,𝑊 )=𝑊𝑜𝑟𝑘𝐷𝑜𝑛𝑒 ( 𝐽 )𝑡𝑖𝑚𝑒𝑡𝑎𝑘𝑒𝑛(𝑠)

The law of the conservation of momentum states the total momentum in a system of objects always stays the

same.

Big Fish – Before collision is zero as it has zero

velocity

Small Fish – Before collision is

1 x 5 = 5 kg m/s

Mass of big fish is 4 kgMass of small fish is 1 kg

Speed of small fish is 5 m/s

Momentum (kg m/s) = mass (kg) x velocity (m/s)

Both Fish – After collision must equal the total momentum before the collision i.e. 0 + 5 = 5 kg m/s

So 5 = 5(combined mass of fish 4+1) x new speedSo new speed = 5/5 = 1 m/s

Car safety, when a car crashes the forces, energy and momentum involved can easily become fatal. The way to

reduce the force involves increasing the time it takes for the object to slow down, because: .

𝐹=𝑚𝑣−𝑚𝑢

𝑡

Making the time bigger makes a

smaller change of momentum

If the acceleration is small then the

force is also smaller

A person weighing 60kg stopping in 0.1s from 14m/s (or 30mph) endures a force of 8400N. This is equivalent to 14

times the force of gravity. If the time to stop is increased to 1s the force is 840N, equivalent to 1.4 times the force of

gravity. Seat belts stretch and increase the time before the

wearer comes to a stop

Air bags slow the occupant down

slowly, increasing the time for the

occupant to come to a stop

Crumple zones slow the whole vehicle

down slowly, increasing the time

for everything to come to a stop

Task for you !

With the materials in front of you create the greatest animal that never lived. You must be able to explain its features and characteristics.

What can you

remember?

Brakes have been applied and car is slowing. Affected by:1. Road conditions (icy or wet)Note: this affects the friction between the road and tyre.2. Brakes are worn3. Speed of car4. The mass of the car

Driver is thinking/reacting before deciding to apply the brakes. Affected by:1. Drugs (alcohol/illegal)2. Tired3. Distracted (mobile etc)Or anything that slows your time to react.

12

STOPPING DISTANCE

Energy Transferred means the same thing as Work Done;Energy transferred = Work DoneBoth are measured in joules (J)

There are different kinds of energy that cannot be destroyed or created, they can however be transferred

from on type to another. A battery for example transfers chemical energy to electrical energy

Most Kids Hate Learning G C S E Energy Namesagnetic

inetic

eat ight

ravitational

hemical

ound

lectrical

lastic

uclear

1 2

3

4

5 6 7

8

Energy transferred = Work Doneis calculated;

Work Done (J) = Applied Force (N) x distance moved (m) (in direction of force)

W = F x d

W = F x dW = 500 x 2W = 100J

NB: 1kg = 10N

1 2 3

Gravitational Potential Energy (GPE) is energy an object has because of its height in a gravitational field.

Kinetic Energy (KE) is energy an object has because it is moving.

Remembering that energy cannot be destroyed or created, they can however be transferred gives us an easy example to see these energies at work. If a cannon ball is falls from 5m it converts GPE to KE as it falls and in this case then to sound!

1

2 3

4

5

6 7

8

Power is a measure of how fast you can do work or how fast energy is transferred.

Take these two cars they both have a 1.6 litre turbo engine and the same chemical energy power source (petrol). The one on the right uses 1 litre of fuel for

every 325m where as the one on the left uses 1 litre of fuel for every 18150m.

𝑃𝑜𝑤𝑒𝑟 (𝑊𝑎𝑡𝑡𝑠 ,𝑊 )=𝑊𝑜𝑟𝑘𝐷𝑜𝑛𝑒 ( 𝐽 )𝑡𝑖𝑚𝑒𝑡𝑎𝑘𝑒𝑛(𝑠)

1 2

3

4

56

7

The law of the conservation of momentum states the total momentum in a system of objects always stays the

same.

Big Fish – Before collision is zero as it has zero

velocity

Small Fish – Before collision is

1 x 5 = 5 kg m/s

Mass of big fish is 4 kgMass of small fish is 1 kg

Speed of small fish is 5 m/s

Momentum (kg m/s) = mass (kg) x velocity (m/s)

Both Fish – After collision must equal the total momentum before the collision i.e. 0 + 5 = 5 kg m/s

So 5 = 5(combined mass of fish 4+1) x new speedSo new speed = 5/5 = 1 m/s

1

2 3

4 5 6

78

Car safety, when a car crashes the forces, energy and momentum involved can easily become fatal. The way to

reduce the force involves increasing the time it takes for the object to slow down, because: .

𝐹=𝑚𝑣−𝑚𝑢

𝑡

Making the time bigger makes a

smaller change of momentum

If the acceleration is small then the

force is also smaller

1 2

3

A person weighing 60kg stopping in 0.1s from 14m/s (or 30mph) endures a force of 8400N. This is equivalent to 14

times the force of gravity. If the time to stop is increased to 1s the force is 840N, equivalent to 1.4 times the force of

gravity. Seat belts stretch and increase the time before the

wearer comes to a stop

Air bags slow the occupant down

slowly, increasing the time for the

occupant to come to a stop

Crumple zones slow the whole vehicle

down slowly, increasing the time

for everything to come to a stop

1

2

3

4