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ICSE Class 10 Answered

Hi, Solve this question. A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:  (a) the work done by the engine.  (b) the power of the engine.
Asked by anubhutiupadhaya | 18 Mar, 2023, 08:18: PM
answered-by-expert Expert Answer

Given that,

Initial speed vi = 18 cross times 1000 over 3600= 5 m/s

Final speed vf =54 cross times 1000 over 3600  = 15 m/s

(a)

Now,

Acceleration, a = (vf - vi)/t

= (15 - 5)/5 = 2 m/s2

The force can be calculated using Newton’s second law: F = ma, where m is mass of car:

F = 120 × 2 = 240 N  

d= vit + ½ × at2

=55+1/2225

∴ d =50m   

The work done by the engine, W = F × d,

= 240× 50m =12000 J

(b)

The power of engine, P =W/t

P = 12000/5 =2400W

Hence, the work done by the engine is 12,000 J and its power is 2400 W.

Answered by Jayesh Sah | 18 Mar, 2023, 08:21: PM

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