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At a certain time interval, a lift of 400 kg moving varies its speed 4 m / s to 6 m / s. Determine the value of work in Joules, the force on the lift range.

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There is a force on the lift exerted by some motors etc. due to which it accelerates and decelerates. Let us say its acceleration is 'a' upwards. let time interval be t1.

a = (6 m/s - 4 m /s )/ t1 = 2/t1

distance traveled in t1 = 4 t1 + 1/2 a t1 * t1 = 5 t1

there is change in PE : 400 * g * 5 t1 positive if lift moved upwards.

change in Kinetic energy = 1/2 * 400 (6*6 - 4 * 4) = 1000 Joules positive

total change in energy = 2000 g t1 + 1000

force on the lift = m a = 800 / t1

a = (6 m/s - 4 m /s )/ t1 = 2/t1

distance traveled in t1 = 4 t1 + 1/2 a t1 * t1 = 5 t1

there is change in PE : 400 * g * 5 t1 positive if lift moved upwards.

change in Kinetic energy = 1/2 * 400 (6*6 - 4 * 4) = 1000 Joules positive

total change in energy = 2000 g t1 + 1000

force on the lift = m a = 800 / t1