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A Level Specific Heat Capacity Questions

 

Q7. A bicycle and its rider have a total mass of 95 kg. The bicycle is travelling along a horizontal road at a constant speed of 8.0ms-1.

(a) Calculate the kinetic energy of the bicycle and rider.

Ek = ½mv2

Ek = ½ x 95 x 8.02

Ek = 3040 J

(2 marks)

(b) The brakes are applied until the bicycle and rider come to rest. During braking, 60% of the kinetic energy of the bicycle and rider is converted to thermal energy in the brake blocks. The brake blocks have a total mass of 0.12 kg and the material from which they are made has a specific heat capacity of 1200 J kg-1 K-1.

(i) Calculate the maximum rise in temperature of the brake blocks.

60% of the KE = 0.60 x 3040 = 1824 (J)

ΔQ = mcΔθ

1824 = 0.12 x 1200 x Δθ

Δθ = 13 K (12.7 K)

(ii) State an assumption you have made in part (b)(i).

No heat is lost to the surroundings

(4 marks)

(Total 6 marks)