Physics

Question 1

What do you always do when doing a practical experiment?

Answer 1

Record the results in a table

Question 2

If a lamp had to be kept a certain distance away from a thermometer why is it important to measure the height?

Answer 2

To ensure the distance remains a control variable

Question 3

A lamp transfers 18000J, of which, 13320J is transferred usefully. Calculate the efficiency of lamp 2.

Answer 3

13320÷18000=74% Efficient

Question 4

What is the equation that links efficiency, useful energy transfer and total energy transfer.

Answer 4

Efficiency = useful output energy transfer
—————————————–
total input energy transfer

Question 5

Describe the waste energy transfer of a lamp.

Answer 5

Energy is transferred to the thermal store of the surroundings

Question 6

Compare the use of an ordinary bicycle and an electric bike going up a 5 km hill.

Answer 6

Electric is more powerful and has waste energy transferred by the motor as sound as well heat to the thermal store of the surroundings, also, the battery may run out before next hill.

Ordinary is less powerful than the electric motor and transfers heat energy to the surroundings

Figure out why: power of cyclist is 300W & motor produced 250,000J of energy

Question 7

Suggest why a drill is water-cooled as it moves through the rocks in the Earth’s surface.

Answer 7

To reduce friction by lubrication

Question 8

What is the equation that links GPE, mass, gravitational field strength and height?

Answer 8

GPE=mgh

Question 9

Calculate the gravitational potential energy of a 2kg weight lifted 16m above the surface of the rocks.
Gravitational field strength = 10 N/kg

Answer 9

2x10x16=320J

Question 10

What is the equation that links speed, energy and mass

Answer 10

Ek = 1/2xmv^2

Question 11

Calculate the velocity of the 2kg weight just before it hits the rocks when it is dropped from a 16m height

Answer 11

2x16x10 = 320
√320/0.5x2 = 17.9 (m/s)

Question 12

State one assumption you made when you did the previous question

Answer 12

No energy was transferred to the surroundings

Question 13

Why is an abseiling rope tested beyond twice the maximum possible weight when in use?

Answer 13

For safety reasons (so the rope doesn’t break) and so the rope doesn’t exceed it’s elastic limit

Question 14

Calculate the new length of a 7.6m abseiling rope when 4.8x10^2 J of elastic potential energy are stored in the stretched rope. Spring constant on the rope is 9x10^2 N/m

Answer 14

√480/0.5x900=1.033

7.6 + 1.033 = 8.633