Test 11

Question 1

Formula for resultant force.

Answer 1

F= change in p/change in t

Question 2

Explain one other advantage of keeping the surface of the pan shiny.

Answer 2

The shiny surface is a poor emitter of radiation, and so reduces thermal energy losses

Question 3

Explain, in terms of particles, why it is difficult to compress liquids.

Answer 3

Particles are close together and forces between particles is large

Question 4

Explain why the radio transmitter without the wires is a very unstable structure.

Answer 4

a small rotation produces a moment which topples the radio transmitter

Question 5

State the uses of radio waves.

Answer 5

to transmit radio and television programmes, RFID, astronomy, bluetooth

Question 6

Describe the method of generating electric power using hydroelectric power.

Answer 6

Water is kept behind the dam and is released. As the water falls, gpe is transferred to ke. Water turns turbines, which then turns generators.

Question 7

Advantages and disadvantages of hydroelectric power.

Answer 7

safe, clean and reliable way. Short start-up time, so quickly generated when there is demand

people made homeless, wildlife habitats destroyed

Question 8

Explain, in terms of particles, why the rod becomes negatively charged.

Answer 8

electrons are lost by friction from the cloth to the rod, rod gains electrons

Question 9

A negative point charge Z placed near to sphere S, (full of electrons). The charge experiences a force due to the electric field surrounding S. Draw an arrow to show the direction of this force on the charge.

Answer 9

line from sphere, pointing towards Z, through Z

Question 10

Voltage in series and parallel.

Answer 10

V=V1+V2+V3 (series)

voltage is the same everywhere (parallel)

Question 11

Current in series and parallel.

Answer 11

current is the same everywhere (series)

current is split between branches, adding them gives current in power supply (parallel)

Question 12

Resistance in series and parallel.

Answer 12

R=R1+R2+R3 (series)
(fractions for parallel)

Question 13

(Of a circuit) The cylinder is replaced..

Answer 13

R is directly proportional to L

R is indirectly proportional to A

Question 14

An atom of a different element has a nucleon number of 241.
State two differences between the composition of a nucleus of this atom and a nucleus of americium-241.

Answer 14

number of protons and neutrons

Question 15

Explain why α-particles are more strongly ionising than β-particles.

Answer 15

more ke, more charge

Question 16

Using this information, explain the advantage of this long half-life for the use and safe disposal of a household smoke alarm.

Answer 16

low activity, so not hazardous to humans, disposal of old detectors is easy and cheap

Question 17

Describe what happens in the core of a stable star to release energy that is eventually
transferred into space.

Answer 17

hydrogen nuclei fuse to become helium nuclei by nuclear fusion

Question 18

Describe how the observed light is different from when it was emitted.

Answer 18

Light was redshifted. Observed wavelength is longer, because it is shifted towards the red end of the spectrum.

Question 19

State the quantity that astronomers use to determine the speed at which the galaxy is moving away.

Answer 19

change in wavelength due to redshift

Question 20

Perpendicular distance

Answer 20

literally