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Question
The velocity of a car increases from 54 km/hr to 72 km/hr. How much is the work done if the mass of the car is 1500 kg?
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Solution
Given:
Initial velocity of the car (u) = 54 km/hr
= `(54 xx 1000)/3600` m/s
= 15 m/s
Final velocity of the car (v) = 72 km/hr
= `(72 xx 1000)/3600` m/s
= 20 m/s
Mass of the car (m) = 1500 kg
Find: Work done (W)
Formula: Work done (W) = Final kinetic energy - Initial kinetic energy
Calculations:
W = `1/2"mv"^2 - 1/2"mu"^2`
W = `1/2"m"("v"^2 - "u"^2)`
W = `1/2 xx 1500(20^2 - 15^2)`
= `1/2 xx 1500(400 - 225)`
= `1/2 xx 1500 xx 175`
W = 131250 J
Work done to increase the speed of the car 131250 J.
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