# physics 2a revision summary

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- Created by: 12rmccarthy
- Created on: 05-06-17 11:06

whats the difference between speed and velocity

speed is just how fast you're going but velocity must also have a direction specified

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explain how to calculate speed from a distance time graph

calculating the gradient

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write down the formula for acceleration and work out the acceleration of an object from rest to 14m/s in 0.4 seconds

v-u/t. 14/0.4= 35m/s^2

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what are the typical points on a velocity time graph

distance is area under graph, gradient is acceleration, horizontal is constant speed, curve is changing acceleration

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explain the difference between mass and weight and give their units

mass is the amount of 'stuff' in an object- measured in kg. weight of an object is just the force of gravity pulling it towards the centre of the earth

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if an object has 0 resultant force on it can it be moving? or can it be accelerating?

it can be moving if it was already moving but it cannot accelerate it can only move at a constant speed

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what is the formula relating resultant force and acceleration? and calculate the acceleration of a trolley with mass of 4kg and a resultant force of 30n

F=mxa acceleration= 30/4= 7.5m/s^2

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state what size reaction force you will feel if you interact with an object

an equal and opposite reaction force

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what is terminal velocity

the constant speed that a freely falling object eventually reaches when the frictional force is equal to the accelerating force- therefore preventing any further acceleration

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what are the 2 different parts of the overall stopping distance of a car

thinking distance and stopping distance

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what is the formula for work done

work done= force x distance.

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whats the formula for kinetic energy

0.5 x mass x speed^2

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what connects kinetic energy and gravitational potential energy

kinetic energy gained = potential energy lost (so e.g. kinetic energy when object hits the ground = gpe at top)

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what connects work done and kinetic energy

kinetic energy transferred= work done by brakes

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what happens to an object that is stretched beyond its limit of proportionality

the material will be permanently stretched

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if the total momentum of a system before a collision is zero what is the total momentum of the system after the collision

0 kg m/s as conservation of momentum states that total momentum before an event is total momentum after the event

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what is the advantage of using regenerative braking systems

rather than converting the kinetic energy into heat energy, the brakes put the vehicles motor into reverse so the wheels turn backwards and slow. then the motor converts KE into electrical energy to be stored as Chem energy- so no energy wasted

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explain how seat belts, crumple zones, side impact bars and air bags are useful during a crash

seat belts- absorb ke and stretch so increase impact time, crumple zones- increase impact time and convert some ke into other forms when shape changes, SIB- divert ke away from passengers to other areas, air bags- increase impact time

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what causes the build up of static electricity

electrons being transferred between two insulating materials when they are rubbed together- making each material charged

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what happens when the resistance of a component increases

current flowing through reduces

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explain how resistance of a component changes with temperature

when an electrical charge flows through a resistor, some elec energy is transferred to heat energy so the ions in the resistor gain more KE and vibrate more, which makes it harder for the charge carrying electrons to flow through, so less current

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give 3 applications of LED's

digital alarm clocks, appliances to show if they are switched on and traffic lights

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describe how resistance of an LDR varies with light intensity and give a use of an LDR

as light intensity increases, resistance decreases- automatic night lights

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state features of a series circuit

components connected in a line- end to end. current is the same everywhere, potential difference is shared (so voltages add up) and resistance is shared (so resistances add up)

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state features of a parallel circuit

connected side to side, P.D is the same everywhere, current is shared (currents add up)

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## Other cards in this set

### Card 2

#### Front

explain how to calculate speed from a distance time graph

#### Back

calculating the gradient

### Card 3

#### Front

write down the formula for acceleration and work out the acceleration of an object from rest to 14m/s in 0.4 seconds

#### Back

### Card 4

#### Front

what are the typical points on a velocity time graph

#### Back

### Card 5

#### Front

explain the difference between mass and weight and give their units

#### Back

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