Y11 Boron

H10 Working with nuclear

radiation

1 (a) Axes labelled correctly, 1

plots correct. 2

Deduct one mark per mistake up to a maximum of 2.

(b) Nuclear power stations have had a negligible

effect on the amount of background radiation. 1

(c) Radiation constantly present around us. 1

(d) (i) Space. 1

(ii) Rocks/soil. 1

(iii) Soil. 1

(iv) Rocks. 1

Total 9

2 (a) A charged atom or molecule. 1

(b) The ray strips an electron from an atom, leaving

it positively charged. 1

The electron attaches to a nearby atom making

it negatively charged. 1

Total 3

3 (a) Cooling water/laboratory equipment/used

protective clothing.

Any one. 1

(b) (i) If the waste got wet the water would

become radioactive 1

and end up in streams, rivers, wells, the

water table, 1

where it would affect plants and animals

(including humans). 1

(ii) Clay is impervious to water. 1

(c) (i) 24000 years. 1

(ii) 48000 years. 1

Total 7

4 Tracers/radiotherapy/sterilising medical

equipment/radioactive dating/measuring thickness.

Any two. 1

Total 1

y12 Homework on Resistors in Series and Parallel

All answers in ohms

series 55 parallel 5
series 10 parallel 2.4
series 29 parallel 2
A series circuit has only one current path and the potential has to be divided between the components. As a result the current is low and therefore by Ohm’s law the resistance is high.
A parallel circuit has one current path for each resistor and each has the same. As a result the current is high and therefore by Ohm’s law the resistance is low.
12.9
series 10 parallel 6
A&B 1.6 B&C 2.1 A&C 2.5
Extra 12 and 8

This homework is now closed

Y9 Bream Homework

Pressure

1. Why do stiletto heels damage floors?
Stiletto heels have a very small surface area. As a result the person’s weight is spread over a small area and there is high pressure exerted on the floor

2. Why is thick padding added to the straps of some rucksacks?
The padding increases the area of the straps. The weight of the rucksack is spread over a larger area. This reduces the pressure exerted on the person’s shoulders.

3. Why do bulldozers have caterpillar tracks?
This increases the area in contact with the soft ground. The large weight of the bulldozer is spread over a larger area so there is less pressure and the bulldozer is less likely to sink into the mud.

4. Why do loaded plastic shopping bags dig into your hands?
The surface area in contact with your hand is small. The weight of the shopping in the bag is concentrated over a small area so the pressure on your hands is high

5. Why do knives cut?
The blade of a knife has a small area. When you push down on the knife the force is concentrated on a small area. This produces a very large pressure under the blade.

6. What do you do when you sharpen knives?
The area under the blade is made smaller increasing the pressure exerted by a force of the same size.

7. Why must workmen walk on ladders on top of a weakly constructed roof?

The area of the ladder in contact with the roof is large. This spreads out the weight of the workman exerting a low pressure on the roof.

8. Why do some heavy lorries have 8 rear wheels?
The weight of the lorry is spread over a lager area exerting a lower pressure on the road

9. Why can an Indian Fakir lie on a bed on nails if it contains a large
number of nails ?
The surface area of a large number of nails is high. The weight of the fakir is spread over a large surface area. The pressure exerted by each single nail is low.

10. Why is it less painful for small children to walk barefoot on pebbles than it is for adults?

The child weighs less than the adult. As a result the pressure exerted by a single pebble of the same area is lower on the foot of a child than the foot of an adult