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IBDP Physics- A.3 Work, energy and power- IB Style Questions For SL Paper 2 -FA 2025

IBDP Physics SL Paper 2 -FA 2025- All Chapters

Question

(a) A car of mass \(1600\,\text{kg}\) starts from rest and accelerates. The graph illustrates how the resultant force \(F\), acting in the direction of motion, varies with the distance \(d\) travelled by the car.
(i) State the physical quantity represented by the area beneath the graph.
(ii) Determine the final speed reached by the car.
(b) Another car moves along a horizontal road at a steady speed of \(45\,\text{m}\,\text{s}^{-1}\). Its engine delivers a power output of \(140\,\text{kW}\). The resistive force \(F_d\) acting on the car is given by \(F_d = c v^2\), where \(v\) is the speed of the car and \(c\) is a constant. Calculate the value of \(c\). State the fundamental SI unit of your answer.

Most-appropriate topic codes (IB Physics):

• Topic A.3: Work, energy and power — parts (a) and (b)
▶️ Answer/Explanation
Detailed solution

(a)
(i) Work done.
(ii) Area \(W = (3.0 \times 10^{3} \times 60) + (0.5 \times 3.0 \times 10^{3} \times 40) = 2.4 \times 10^{5}\,\text{J}\).
Using \(W = \Delta E_k = \tfrac{1}{2} m v^2\):
\(v = \sqrt{\dfrac{2 \times 2.4 \times 10^{5}}{1600}} \approx 17\,\text{m}\,\text{s}^{-1}\).

(b)
Driving force \(F = \dfrac{P}{v} = \dfrac{140 \times 10^{3}}{45} \approx 3111\,\text{N}\).
Since \(F = F_d = c v^2\):
\(c = \dfrac{3111}{45^2} \approx 1.5\,\text{kg}\,\text{m}^{-1}\).

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