YR13 BTEC Physics Unit 5
Diagnostic Week 3
Name:_____________________________________
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Questions
Q1.
A pan of water is heated from room temperature until the water boils.
(i) The temperature of the water increases by 80 K from room temperature to boiling point.
The energy needed to heat the water to boiling point is 5.0 × 105 J.
Calculate the mass of water heated.
(3)
The specific heat capacity of water is 4200 J kg
Use the equation: Q = m c ΔT
Show your working.
−1
−1
K
mass of water = ........................................................... kg
(ii) The water in the pan boils and forms steam.
Explain what happens to the intermolecular structure when water forms steam.
Your answer should refer to intermolecular forces and intermolecular spacing.
(4)
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(Total for question = 7 marks)
Q2.
(i) A boiler gives out 3.5 × 109 J of energy to heat a home each year.
To produce this amount of energy, the boiler takes in 2.9 × 1010 J.
(2)
Calculate the efficiency of the boiler.
Use the equation:
Show your working.
efficiency of boiler = ...........................................................
(ii) Give a value for an amount of energy that the boiler should take in to increase its efficiency.
(1)
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(Total for question = 3 marks)
Q3.
Figure 2 shows a student doing work by lifting weights.
The student in Figure 2 uses a force of 600 N to lift the weights.
The weights are lifted from the floor to a height of 0.75 m.
Calculate the work done in lifting the weights.
(2)
Use the equation: W = F × Δx
Show your working.
work done = ........................................................... J
(Total for question = 2 marks)
Q4.
Figure 3 shows three lifts in a building.
The lifts in the building rise through a height of 0.5 km.
The weight of one lift cabin is 12 500 N.
(i) Show that the motor does approximately 6 000 000 J of work raising the lift cabin 0.5 km.
Use the equation: W = FΔ x
(3)
Show your working.
work output of the motor = ........................................................... J
(ii) The efficiency of the lift motor is 0.85.
Calculate the work input to the motor when raising the lift cabin.
If you did not get an answer for (i), use the value 6 000 000 J for the work output.
(3)
Use the equation:
Show your working.
work input to the motor = ........................................................... J
(Total for question = 6 marks)