Question

According to the theory of force-velocity principle, please discuss the difference of force output/generation between 1 cycle of bicycle pedaling in moderate speed and a maximum football kickoff

Answer 1

We need to compare the forces involved in a football kick and bicycle pedaling

Fastest soccer ball kick: 210 kmph. Let us use this. Mass of ball = 0. 45 kg

F = ma

The foot is in contact with the ball for approximately a second. If we assume that the force is applied constantly at this time, then the ball goes from 0 to 210 kmph in 1 second. The acceleration is thus:

a = (v_fin -v_initial) / t =( 210 - 0 )/1 = 210 m/s^2

Thus, the force to be generated is: F = ma = 0.5 * 210 = 105 N

Next, a moderate speed bicycle.

A bicycle won't work without friction between the wheel and the ground. Let the mass of the person be m_p and the cycle m_c.

For an object moving on the ground, the frictional force is given by the formula:

F_fric = k M g

where k = coefficient of friction (that varies from 0 to 1), M is total mass, g is acc. due to gravity= 9.81 m/s^2

If the person weighs 100 kg and the cycle is 15 kg, the total is 115 kg.

In moderate speed , k is approximately 0.4 (kinetic friction is lesser than static friction). Also, since it is a moderate speed, the drag effects given by the surrounding air can be neglected.

Thus, the frictional force is F_fric = 0.4 *115*9.81 = 451.26 N