Respuesta :
The average force of air resistance is; 186 N
The force of friction underwater if she reaches a depth of 2.5 m before
stopping is; 1734 N
How to find the average force?
(a) Without air friction, the velocity that she will achieve when entering the water will be gotten by the formula;
V = √(2gh)
We are given h = 15 m. Thus;
V = √(2 * 9.8 * 15)
V = 17.15 m/s .
However, we are told that she reaches a speed of 14.0 m/s just before entering the water. Thus;
Loss in K.E. = (Average force * distance)
Average Force = Loss in K.E./distance
Formula for kinetic energy is;
K.E. = ¹/₂mv²
Thus;
Average Force= [(¹/₂ * 57(17.15² – 14²)]/15
Average force = 2793/15 = 186 N
(b) To get the force of friction underwater, we will use the formula;
(Friction force + buoyancy force) * (distance below water surface ) = Kinetic energy when entering water
Thus;
(F_f + 500) * (2.5) = (¹/₂ * 57 * 14²)
F_f + 500 = 2234 N
F_f = 1734 N
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