Question

A truck weighing 1000 kg changes its speed from 36 km/h to 72 km/h in 2 minutes. Calculate:
(i) the work done by the engine and
(ii) its power.
(g =10 m s^-2)

April 23, 2024

Answer

Mass (m) = 1000 kg

Initial velocity (u) = 36 km h^-1 = 10 m s^-1

Final velocity (v) = 72 km h^-1 = 20 m s^-1

Time = 2 min = 120 s

Distance (s) = $v^2 - u^2\over 2a$

(i) Work done = Force × distance

= m × a × $v^2 - u^2\over 2a$

= 1000 × $20^2 - 10^2\over 2$

= 500 × (400 – 100) = 15000 J

(ii) Power = $150000\over 120$ = 1250 W

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