• (because) like charges repel A boy combs his hair using a plastic comb. His hair becomes positively charged. Explain what happens to the boy’s hair when it becomes positively charged. Either • loss of a negative (1) • electron (1) Or • hair’s repel (1) • (because) like charges repel

The boy puts his charged comb near some small pieces of paper The boy puts his charged comb near some small pieces of paper. Explain what happens. • paper is picked up (1) • charged objects attract uncharged (1) • charges separate on paper(1) • opposite charges attract(1) • weight is less than electrostatic force (1)

substitution (1) 54 × 10 × 5 evaluation (1) 2700 The mass of the water skier is 54 kg. At the top of the jump, she is 5 m above the water level. Calculate the amount of gravitational potential energy she gains in rising 5 m. Gravitational field strength = 10 N/kg substitution (1) 54 × 10 × 5 evaluation (1) 2700

When the water skier reaches the top of the ramp, she lets go of the rope. Describe the energy changes that happen between the skier leaving the ramp and reaching the top of the jump. • (some) KE at the ramp (1) • is transferred to GPE at top(1) • still has some KE at top (1) • some energy lost due to air resistance (1)

Cobalt-60 is radioactive. It emits beta radiation and gamma radiation Cobalt-60 is radioactive. It emits beta radiation and gamma radiation. Describe the differences between beta radiation and gamma radiation. • beta (radiation) is electron(s)(1) • beta has mass (1) • beta has (negative) charge (1) • beta is a better ioniser (1) • beta is less penetrating (1) • gamma radiation is electromagnetic (1) • wave (1) • gamma travels at a speed of light (1) • gamma is just energy (1)

Fission and fusion are two different types of nuclear reaction Fission and fusion are two different types of nuclear reaction. Describe the similarities and differences between nuclear fission reactions and nuclear fusion reactions. Similarities (S): • involve nuclei • involve particles colliding • energy released • can cause explosions/rapid release of energy Differences (D): Fission • splitting • of heavy nucleus • by neutron • chain reaction • products radioactive • used in power stations at present • rate can be controlled Fusion • joining smaller nuclei • to form larger nucleus • occurs in stars • needs very high temperature and/or pressure and/or particle density • because of like charge repulsion

Scientists have changed their ideas about the hazards from radioactive sources. Describe how their ideas have changed since radioactivity was first discovered. • used to be thought beneficial (1) • now known to be extremely {dangerous/hazardous} (1)

When a charge flows in a resistor, the resistor becomes hot. Explain why the resistor becomes hot. • electron collision (1) • (in the/and the) lattice (1)

The thermal energy released in the reactor is used to generate steam The thermal energy released in the reactor is used to generate steam. Describe how the steam is used to generate electricity. • steam {drives/turns} turbine (1) • (which){drives/turns/powers} generator (1)

Energy is released by a nuclear chain reaction. Describe how the fission of a uranium-235 nucleus can start off a chain reaction.. You may draw a diagram to help with your answer. neutron {hits / splits / is absorbed by} uranium (nucleus)(1) • producing more neutrons (1) • at least one neutron can {hit /split / be absorbed by} other uranium (nuclei) (1)

Barium-142 emits beta radiation.Beta radiation is ionising. Explain what happens when beta radiation ionises. • removes electrons (1) • from atoms (1)

A fusion reaction does not have radioactive products. However, it needs large amounts of energy to make it happen. Explain why large amounts of energy are needed to make a fusion reaction happen. • nuclei are positively charged (1) • need enough energy to overcome repulsion (1)

The graph shows how Christine’s velocity changes from the time she leaves the plane until she reaches terminal velocity. Explain, in terms of forces, why her velocity changes as shown in the graph.

Forces acting • weight down • air resistance up (opposing motion) Forces during fall • weight constant • air resistance increases • with speed • resultant force = W – R Effect on shape of graph • at start, resultant force is large so acceleration large / gradient steep • mid resultant force decreasing so acceleration decreasing / gradient decreasing • terminal velocity, resultant force is zero so acceleration zero / gradient zero

Explain what half-life means. Allow for atoms: isotope / element / nuclei / (radioactive) substance /particles/(radioactive) material/radiation/count rate/Bq/activity/radioactivity time for half of the atoms to decay (2) time for the activity/count rate to drop to half (of original value) (2) time for ½ of it to decay (1)

A teacher decides to model how a machine checks the level of the liquid in medicine bottles. The machine uses a radioactive source to sound an alarm when the level of liquid becomes too low. He sets up the arrangement shown. The piece of card can be moved up and down between the lamp and the detector. Each part of the teacher’s arrangement corresponds to a part of the machine. By comparing the parts of the teacher’s arrangement to the parts of the machine, discuss how effective this model is.

Model components related to actual machine • lamp – radioactive source (β- source) • sensor (LDR) – Geiger counter arrangement • card – liquid in bottle Interaction of components related to working of machine • rising of card - more liquid in bottle • rising of card – less light – higher resistance – smaller current / reading – circuit switches on if too much light • greater absorption gives less radiation to detect • machine discards bottle if too little liquid, model does not