paper2 phys mistakes

Internal contamination of the human body means radioactive material is inside the body. Explain how risk from internal contamination is different to external irradiation by a source of alpha radiation [4]

alpha radiation has a low penetrating ability [1]

(so externally) alpha radiation is stopped by skin (so is low risk). allow absorbed for stopped [1]

internally, alpha radiation is absorbed by living tissue / organs. allow (internal) contamination will increase the radiation dose [1]

(as) alpha radiation is highly ionising [1]

(internal) contamination will cause greater (risk of) harm to cells / tissues / organs / DNA / genes [1]

allow contamination causes greater chance of developing cancer [1] allow greater chance of mutations [1]

PP2022

B

PP2022

Any three from:

Use a force meter/newton meter to measure (pulling) force [1]

Measure distance (moved) using a ruler/metre rule/ measuring tape [1]

Repeat experiment with different masses (on the wooden block) [1]

Use work done = force x distance [1]

PP2022 There are three different isotopes with the following half-lives:

4 minutes 6 hours 18 days

The doctor chooses the isotope with a half-life of 6 hours. Suggest two reasons why 6 hours is the most suitable half-life [2]

(Idea that half-life is) long enough to allow the isotope to circulate around the body / ORA for ideas about half-life of 4 minutes [1]

(Idea that half-life is) short enough for less damage/harm (to patient’s cells/body) / patient will not be contaminated/radioactive for a long time / ORA for ideas about half-life of 18 days [1]

PP2022

PP2022 Fig. 21.1 shows how the energy output per second of a wind turbine depends on the wind speed. Suggest a reason why energy output per second is zero when the wind speed is:

1 Less than 3.5 m / s.

2 Greater than 25 m / s.

1 Not enough wind/force/energy/speed to turn the turbine [1]

2 (Speed too high so) could damage the turbine / turbine is shut down to stop damage/for safety reasons [1]

PP2022 The potential difference across the primary coil is 900 V. The potential difference across the secondary coil is 36 000 V. The current in the primary coil is 2800 A.

Explain why the use of this transformer reduces power loss in the national grid [3]

It is a step-up transformer / to increase p.d. [1]

Decrease current (in power lines) [1]

less energy wasted/lost / less heat in power lines / less thermal transfer [1]

(idea that) power loss depends on current² [1]

PP2022

(Speed is constant because) (resultant) force is perpendicular to direction of motion / (resultant) force is a centripetal force / there is no displacement in direction of force [1]

No work is done on the planet [1]

(Velocity is changing because) the direction is changing [1]

(Resultant force) provided by gravitational pull of the sun (causes the direction of motion to change) [1]

(So) planet is accelerating [1]

PP2022 Explain why the speed of a planet changes when the radius of orbit changes. [2]

Smaller radius or closer to the Sun means larger (gravitational/centripetal) force/pull [1]

(smaller radius or closer to Sun or larger gravitational/centripetal force means) larger acceleration/speed [1]

OR

Closer orbits have a lower GPE [1]

(closer orbits have) higher KE [1]

Before the power supply was switched on, the thermometer was used to measure the temperature of the iron block. The student left the thermometer in the iron block for a few minutes before recording the initial temperature. Suggest why. [1 mark]

so the thermometer temperature was the same as the temperature of the iron block

Calculate the charge flow through the 12 V battery when the battery transfers 5010 J of energy. [3 marks]

E = Q V

417.5

Total internal energy =

KE + PE

Fig5 is a graph for hydroelectric generator. A solar power system is installed in the remote village in addition to the hydroelectric generator. Explain why this improves the reliability of the electricity supply to the village. Use information from Figure 5. [2 marks]

in the summer the power output from the hydroelectric generator is lower but the solar power output would be greater

so less variation in total power output (which improves the reliability of the supply)

define half life

time for the number of nuclei to halve

Isotope - Halflife

Nitrogen-18 : 0.62sec

Nitrogen-17 : 4.17sec

Fluorine-17 : 64.37sec

Fluorine-18 : 6584.34sec

A sample of fluorine-17 has an activity that is one quarter of its original activity. Calculate the age of the sample of fluorine-17. [2 marks]

2 half-lives 128.74 (s)

Isotope : Halflife

Nitrogen-18 : 0.62sec

Nitrogen-17 : 4.17sec

Fluorine-17 : 64.37sec

Fluorine-18 : 6584.34sec

All of the isotopes in Table 1 emit beta radiation. Explain which isotope would cause the biggest risk to a person’s health based only on the half-life of each isotope. [3]

nitrogen-18

greatest activity

(so) greatest dose of radiation absorbed (per second)

Workers in nuclear power stations are monitored to check the radiation they emit. A worker stands 1 cm away from a radiation detector. The amount of radiation the worker emits is recorded. Explain why the worker needs to stand close to the radiation detector. [2 marks]

some radioactive materials emit alpha radiation

which has a (very) short range (in air)

In positions A and B the baby is stationary. Describe the energy transfers as the baby moves from position A to position B. [3 mark]

GPE → KE some EPE → EPE

In one position the extension of the spring is 8.0 cm. The elastic potential energy stored by the spring is 4.0 J. Calculate the spring constant of the spring. Use the Physics Equations Sheet. [4]

e = 0.080 (m)

4.0 = ½ × k × 0.0802

k = 4.0 (0.5 × 0.0802 )

k = 1250 (N/m)

How is the Bohr model of the atom different from the nuclear model of the atom? [1 mark]

in the Bohr model the electrons orbit (the nucleus) at specific distances (whereas in the nuclear model the electrons can orbit at a continuous range of distances)