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Physics
GCSE

A car of mass 1000 kg is travelling at 15 m/s. The driver applies the brakes for 4 seconds, slowing the car to 5 m/s. What is the average power output of the brakes over the 4 seconds? Assume there are no other forces acting on the car.

Kinetic Energy, EK=(1/2)mv2. Energy is conserved, so the work done by the brakes, W, must be equal to the change in kinetic energy of the car, ∆EK. Therefore: W = ∆EK = (1/2)1000(15

AH
Answered by Adam H. Physics tutor
8680 Views

If a box full of feathers and a box full of bricks were to be dropped at the same time and from the same height, which one would hit the ground first?

In a vacuum (no air):

-Both boxes fall at the same rate and hit the ground at the same time.

-Gravity accelerates all objects equally at 9.8 m/s², regardless of mass.

In re...

AY
12351 Views

Which is heavier, a ton of feathers or a ton of lead?

They're both the same. The feathers would take up a lot more space though! Feathers have a lower density than lead (i.e. for the same volume, feathers are less heavy). In practice, if you drop a tonne of ...

FN
Answered by Francis N. Physics tutor
15789 Views

Define Newton's three laws

1st Law - a body will move with constant velocity or remain at rest unless acted on by a resultant force
2nd Law - F = ma. The rate of change of momentum of an object is equal to the resultant force ...

GW
Answered by George W. Physics tutor
1921 Views

The focal length of the lens is 10 cm. Calculate the power of the lens. State the unit.

first, convert to metres:10cm = 0.1mlens power = 1/focal lengthpower = 1/0.1 =10units are Dioptres, Dso the power of the lens is 10 D

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Answered by Aleks H. Physics tutor
3048 Views

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