A 50-kg toboggan is coasting on level snow. As it passes beneath a bridge, a 20-kg parcel is dropped straight down and lands in the toboggan. If KE₁ is the original kinetic energy of the toboggan and KE₂ is the kinetic energy after the parcel has been added, what is the ratio KE₂/KE₁. A)0.4 B)0.6 C)0.7 D)0.8 E)1

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Quizplus · Accepted Answer

The total mass of the toboggan and parcel after the package is dropped in it is 50+20=70 kg. The velocity of the toboggan doesn't change as it moves at constant speed. Hence, the original kinetic energy of the toboggan is equal to the final kinetic energy of the toboggan and the parcel. Hence, KE₁ = KE₂ Since kinetic energy is proportional to the square of the speed, we have: KE₂/KE₁ = (v12/v11)2 = (m1/m2) = 50/70 = 0.7 Therefore, the answer is C.

A 50-Kg Toboggan Is Coasting on Level Snow