Physics Topic 4, 5, 6 and 7

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T4- What is the formula for stopping distance?
Thinking distance + braking distance
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T4- What can affect the thinking distance?
The speed of the vehicle, as the momentum will be higher. reaction time as this can be slowed by drugs alcohol or lack of sleep.
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T4- What can affect the braking distance?
The speed of the vehicle, as when travelling faster, it is harder to stop. The mass of the vehicle as this also affects the momentum of the vehicle. The quality of the brakes/surface of the road as this can increase/decrease friction.
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T4- What is the formula for momentum?
Momentum (kgm/s) = mass (kg) x velocity (m/s)
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T4- Why/how to safety features in a car work?
Crumple zones crumple on impact increasing the time for the momentukm to change to zero. Seatbelts and airbags also work in this way. Force= change in momentum/time taken. Dividing by larger number= smaller force.
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T4- What is the fact to remember when calculatin collisions/explosions?
That momentum before= momentum after.
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T4- Moment=?
Moment (Nm) = Force applied (N) x perpendicular distance (m)
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T4- What is the method to find the centre of gravity?
1) suspend the shape and plumb line from the same point. 2) When the object is stationary, draw along the plumb line. 3) Do the same but from different pivot points. 4) Where the lines cross, this is the centre of gravity.
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T5- What is a fact to remember when answering questions about moments?
Total anticlockwise moment = total clockwise moment
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T5- On a light beam, which support will provide the most support?
The beam closest to the object.
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T5-What happens when the moments are not equal?
There is a resultant force.
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T5- What dies Hooke's Law state?
That extension is proportional to the force applied. (helical springs, metal wires etc where the material will stretch immediately without snapping.)
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T5- When investigating this, what would you measure?
The extension of the material by measuring the change in length each time from the original length.
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T5- What does the point where the gradient of the line changes on an extension graph show?
It shows the elastic limit of the object , where hooke's law is no longer obeyed.
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T5- What is elastic behaviour?
When an object returns to its original shape after being extended.
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T5- What is a galaxy?
A collection of billions of stars. The distance between stars is millions of times greater than the distance between planets.
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T5- What is the universe?
It is a collection of billions of galaxies. The distance between galaxies is millions of times greater than the distance between stars
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T5- How does gravity cause orbiting?
Because orbits are the balance between he forward motion of an object and the force pulling it inwards.
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T5- What examples of orbiting does gravity induce?
The orbiting of moons of planets, planets orbiting the sun, comets orbting the sun and artificial satellites orbiting the earth.
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T5- What is different about the planets nearer to the sun?
Their orbiting period is much shorter (fatser orbit,) as the forces of attraction between the masses is stronger, so the forward force of the planet is faster to balance this.
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T5- Describe the orbit of a comet.
It is a longer period of time since it travels to the outer edges of the solar system, however when it approaches the sun, the orbit is faster due to the greater force of attraction.
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T5- What is the formula for orbital speed?
orbital speed = 2 x pi x orbital radius/ time period.
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T6- Where do each of the three wires in a plug go, and what colour are they represented by?
bLue to the Left, (Neutral). sTriped to the top (earth,) bRown to the right (live.)
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T6- What does a safe plug look like?
The wires are firmly screwed in with nothing bare, cable grip fastened on the cable's outer layer.
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T6- What are some safety precautions when using a plug?
Make sure that live parts aren't exposed to prevent shocks, (cable must not be frayed.) Make sure the cables aren't too long to stop a trip hazard. Check that there is no water around the sockets.
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T6- How does electricity flow?
In through the live wire and out through the neutral wire. The live wire alternates between high positive and high negative voltage of 230 V.
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T6- When must an appliance be earthed?
If it has a plastic casing, then it is double insulated, but if the appliance has metal casing, then it must be attached to the earth wire.
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T7- Explain fusing and earthing.
If the live wire touches the metal casidng, a big current will flow through the live wire, through the metal casing and out down the earth wire. This surge in current blows or melts the fuse. This cuts off the live supply and the appliance is safer.
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They detect a surge in current and break the circuit by opening a switch. Therefore it can be easily reset by flicking a switch and does not need replacing unlike a fuse. they are more convenient.
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T7- How do RCCBs work?
Normally an equal current flows through the live and neutral wires. When the live wire is exposed and touches something, the current flows through the object to the earth. The RCCB detects the difference in current from the two and opens a switch.
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Why can RCCBs be considered as superior in some appliances?
They will open the switch for even smaller current changes, so they protect against shocks that a fuse cannot. They act faster than a fuse, since they break as soon as the current changes.
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What are resistors and what do they do?
They are components in a circuit which heat when electrical energy passes through them, and this is transferred into heat energy. The resistors limit the flow of current in a circuit, and as they heat, this effect becomes even more prolific.
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T7- Name an appliance which uses the heat from resistors.
Toasters have coils with a high resistance so they heat to toast the food.
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T7- What is the formula for electrical power?
Electrical power = current x Voltage
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T7- What is the formula for energy transferred?
Energy transferred= current x voltage x time left for.
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T7- What does an amp rating have to be?
Slightly higher than the normal operating current of the appliance.
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Other cards in this set

Card 2

Front

T4- What can affect the thinking distance?

Back

The speed of the vehicle, as the momentum will be higher. reaction time as this can be slowed by drugs alcohol or lack of sleep.

Card 3

Front

T4- What can affect the braking distance?

Card 4

Front

T4- What is the formula for momentum?

Card 5

Front

T4- Why/how to safety features in a car work?