Physics Answers

In A = B" C" expression, A has a dimension of [LT], and B has a dimension of [L*T| IfC has a dimension of [L'T), find the value of m+n.

3. a. Briefly explain Ohm’s Law (2 marks)

b. A 750 Watt electric convector heater is plugged into a 240 Volt power supply. A trolley

passing over the flex from the heater to the plug has caused the insulation to distort

and has reduced the resistance between the live and neutral wires to 60 Ohms.

(i) What is the rate of heat production (in Watts) at the point where the cable is

damaged? (Please show your calculations.) (1 mark)

(ii) The plug fitted to the heater flex carries a l3 amp fuse, is this the correct rating

for the appliance? (2 marks)

(iii) Would the correctly rated fuse have 'blown' as a result of the fault? (Please

show your calculations.) (1 mark)

b. Several years ago a change in the recognised colour conventions led to phase (live)

cables in industrial three phase power installations being changed from red, yellow

and blue to black, grey and brown. What are the implications for premises that have

not been rewired since that time? (4 marks)

c. Electric lighting is often overlooked as a potential source of ignition. List factors that

might lead to an electric light fitting becoming a source of ignition. (5 marks)

d. List the problems associated with the use of electric adaptors in the workplace and

why their use should be minimised. (5 marks

5. a What is the inverse square law? Give two examples of how it relates to fire safety and

outline a factor other than the spread of heat where the inverse square law also

impacts on fire safety in premises. (6 marks)

b. Illustrate the development of a fire using a drawing of a curve indicating heat

production versus time. (4 marks) Draw two further sketches to indicate the form of

the growth and decay curve that you would expect in the case of: (4 marks)

i) A slow smouldering fire

ii) A firework

c. What is meant by a t2 fire and what are the implications for fire safety? (6 marks)

A rollercoaster is designed to have a car full of riders (total mass = 610 kg) travel along a section of horizontal track at ground level with a speed of 25 m/s and then travel up a ramp, stopping at a height of 22 m.

Calculate the rollercoaster car’s:

(i) Input energy.

(ii) Useful output energy.

(iii) Percent efficiency.

If the rollercoaster was 100% efficient and all of the input energy was entirely transformed into useful output energy, what should have been the maximum height of the car?

A cat chases a mouse across a 1.2 m high table. The mouse steps out of the way and the cat slides off the table at a speed of 7.0 m /s. Where does the cat strike the floor (horizontal distance from table leg)?

A 17 kg block is pulled on a horizontal surface by a force of 205 N that is inclined 29° above the horizontal. If the coefficient of friction is 0.32 and the distance covered by the block was 6.25 meters. What is the work done by the friction force?

Explain the geometrical interpretation of the divergence of a vector field A(x,y,z).

Find the ontward drawn unit to the surface (x-1)²+y²+(z+2)²=9 at the point (3,1,-4)

A racquetball thrown from the ground at an angle of 28° and with a speed of 35 m/s lands exactly 1.6 s later on the top of a nearby building. Calculate the horizontal distance it traveled and velocity just before hitting the building.

What is the mass of a ball that is moving at 25 m/s and has 93.75 kg*m/s of momentum