A trolley of mass 5.0 kg is moving at 1.0 ms to the right. A constant force of 25 N acts to the left for 0.75 seconds. Calculate the change of kinetic energy of the trolley.
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change in kinetic energy of the trolley is 53.91 J.

Explanation:

mass of the trolley, m = 5.0 kg

initial velocity of the trolley, u = 1.0 m/s

external force on the trolley, F = 25 N

time of force action, t = 0.75 s

The final velocity of the trolley at the end of 0.75 s is calculated as follows;

The change in kinetic energy of the trolley is calculated as;

Δ K.E = ¹/₂m(v² - u²)

Δ K.E = ¹/₂ x 5(4.75² - 1²)

Δ K.E = 53.91 J.

Therefore, change in kinetic energy of the trolley is 53.91 J.

no. dot product   =0 when vecs at right angles