Using energy considerations, calculate the average force a 66.0 kg sprinter exer

Question

Using energy considerations, calculate the average force a 66.0 kg sprinter exerts backward on the track to accelerate from 2.00 to 5.00 m/s in a distance of 25.0 m, if he encounters a headwind that exerts an average force of 30.0 N against him. How much gravitational potential energy (relative to the ground on which it is built) is stored in an Egyptian pyramid, given its mass is about 5 times 109 kg and its center of mass is 24.0 m above the surrounding ground? What is the ratio of this energy to the daily food intake of a person (1.2 times A 5.00 times 10^5 kg subway train is brought to a stop from a speed of 0.500 m/s in 0.800 m by a large spring bumper at the end of its track. What is the force constant k of the spring? N/m

Explanation / Answer

3.

F = applied force

f = resisitive force = 30 N

d = distance moved = 25 m

Vi = initial speed = 2 m/s

Vf = 5 m/s

Using work -kinetic energy theorem

(F - f) d = (0.5) m (Vf2 - Vi2)

(F - 30) (25) = (0.5) (66) (52 - 22)

F = 57.72 N

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