# SP1 - SP2

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• Created by: camamkat
• Created on: 12-12-17 09:25
What do vector quantities have that scalar quantatioes don't?
A size and a direction.
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Name 5 scalar quantities.
Speed, mass, distance, time, energy.
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Name 8 vector quantities.
Velocity, weight, displacement, acceleration, force, momentum, current and voltage.
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What is acceleration?
A measure of how fast the velocity is changing/ the change in velocity.
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What is momentum?
A combination of mass and velocity- how difficult it is to stop an object moving.
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What is displacement?
The distance covered in a straight line.
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Why is the displacement usually less that the distance at the end of the journey?
There could be turns and bends in the journey.
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How many Newtons is 100g?
100g is 1N.
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What is gravitational potential energy?
It is the energy an object possesses because of its position in a gravitational field.
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How do you work out the gravitational potential energy of an object?
The product of it's mass (kg), gravitational field strength (10/9.81 accurately) and height (m).
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How do you work out the kinetic energy (J) in an object?
1/2 x m x v² / half x mass x velocity squared.
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Why would the GPE stored by an object lifted by 1 m above the moon's surface be less than when it is lifted about the Earth's?
The gravitational field strength is less on the moon.
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How do you work out momentum (kgms-1)?
mass x velocity / kg x ms-1
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What is the law of conservation of momentum?
momentum before a collision = momentum after.
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Why does a motorcycle travelling at 30m/s have less momentum than a car going at the same velocity?
The motorcycle has less mass, and as the momentum depends on the product of mass and velocity, the higher the mass, the higher the momentum if two objects are moving at the same velocity.
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How is force worked out?
Change in momentum / time.
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How do you work out the stopping distance?
Thinking distance + braking distance.
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Name a factor that the thinking distance is dependant on and why.
It is dependant on the driver's reaction time as the slower the reaction time, the longer the thinking distance will be as they process the problem and decide what to do.
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Name another factor that the thinking distance is dependant on and why.
It is also dependant on the speed of the car as a person with a reaction time of 10 seconds will go further in that ten seconds if he has a faster velocity than another person with a reacton time of 10 seconds who is going slower.
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Why is the overall stopping distance for a car less than the stopping distance of a lorry?
Lorries have greater masses than cars and if the same amount of friction is used to stop a vehicle, a heavier vehicle will travel further than a lighter one.
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What is Newton's First Law?
An object with balanced forces acting on it will stay at rest or in constant motion until an unbalanced force acts on it.
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Give an example for Newton's First Law.
If you are driving a car at a very high speed and hit something, the car will come to a stop because a force has acted on it. If it did not hit another object for a force to act on it, it will continue moving.
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What is Newton's Second Law?
Force = mass x acceleration. Acceleration is produced when an unbalanced force acts on an object. The more mass an object has, the more total force has to be used to move it.
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Give an example for Newton's Second Law.
If you use the same force to push a car and to push a truck, the car will have more acceleration than the truck as the car has less mass.
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What is Newton's Third Law?
For every reaction, there is an equal and opposite reaction. This means that forces are found in pairs. When an object is oushed, it pushes back in the opposite direction equally hard.
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Give an example of Newton's Third Law.
When you are walking on grass, you push on the grass and the grass pushed back on you. There is a friction force between the sole of your shoe and the grass.
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How do you calculate work done?
Force x distance - the useful energy transfer.
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Why is the work done by the brakes in a car the same as all the kinetic energy before braking the car?
The purpose of brakes are to stop all the kinetic energy of a moving object.
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Why does the braking distance times by 4 if the velocity of the car doubles?
The braking distance depends on its kinetic energy and the square of its velocity. The velocity doubles (x2) but has to be squared, so it is 2 squared, which is 4.
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How do you calculate speed?
Speed (m/s) = change in distance (m) / time taken (s)
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How do you work out distance travelled?
Distance travelled (m) = average speed (m/s) x time taken (s)
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How is acceleration worked out?
Acceleration (m/s²) = change in velocity (m/s) / time taken (s) OR a = (v-u) / t
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What do straight lines of a velocity/time graph mean?
The vehicle is moving at a constant velocity.
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What is velocity?
The change in distance per second.
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What do straight lines mean on a distance/time graph?
The vehicle is stationary.
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What is inertial mass?
Inertial mass is the measure of how difficult it is to change the velocity of a moving object and is worked out by the ration 'force over acceleration' or 'f/a'
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What is weight?
Weight is the force that a body experiences due to its mass and the size of the gravitational field it is in. It's measured in N.
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What is mass?
Mass is the measure of the amount of matter that is contained within a three-dimensional space. It's unaffected by the size of the gravitational field it's in and is measured in kg.
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What is resultant force?
The sum of the forces acting on an object. If they are acting in the same direction, add them. If the forces are acting in opposite directions, subtract them from one another.
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Why does circular motion happen?
It happens as there is a force acting inwards along the radius of the circle. This is called the centripetal force and objects move at a right angle to the force.
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What is the human reaction time?
The time between a stimulus occurring and a response. It relates to how quickly the human brain can process information and then react to it.
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What can reaction time be affected by?
Tiredness, distractions, alcohol and drugs, age.
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What is stopping distance?
The total distance over which a vehicle comes to a rest.
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What can the breaking distance be affected by?
The amount of friction between the tyre and the road so the breaking distance increases if the road is icy or wet, or the brakes or tyres are worn out, or if the mass of the car is bigger.
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What are crumple zones?
Crumple zones are a safety feature on vehicles so that if the vehicle hits something, it takes a little time for this crumpling to happen so the deceleration of this vehicle is lessened and the force is also less than if it had a solid front.
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What do airbags do?
Airbags slow down the change in momentum so the force acting on a passenger of a crash is reduced.
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## Other cards in this set

### Card 2

#### Front

Name 5 scalar quantities.

#### Back

Speed, mass, distance, time, energy.

### Card 3

#### Front

Name 8 vector quantities.

### Card 4

#### Front

What is acceleration?

### Card 5

#### Front

What is momentum?