john is walking at such speed so that his kinetic energy is 20 J, what is his speed? It started to rain John runs at a rate of 4.2 m/s find the change in KE.

KE=1/2 m v^2 what is mass?

sorry i forgot.john is walking at such speed so that his kinetic energy is 20 J, what is his speed? It started to rain John runs at a rate of 4.2 m/s find the change in KE if his mass is 50 kg.

To find the speed of John given his kinetic energy, we can use the formula for kinetic energy:

Kinetic Energy (KE) = (1/2) * mass * speed^2

However, to find his speed, we need to know his mass. Without that information, we cannot calculate the speed.

Regarding the change in kinetic energy when it starts to rain and John runs at a rate of 4.2 m/s, we need more information. The change in kinetic energy depends on variables such as time or any other factor that provides information about a change in the system.

To calculate the change in kinetic energy (ΔKE), you need to subtract the initial kinetic energy from the final kinetic energy.

In this case, you are given the initial kinetic energy as 20 J. However, you need the final kinetic energy, which you can calculate using the formula:

KE = 0.5 * m * v^2

Where KE is the kinetic energy, m is the mass, and v is the velocity.

Since you know John's speed, you need to find his mass. Unfortunately, the given information does not provide any clues about John's mass. For now, let's assume his mass is not given, and we will only be able to calculate the change in kinetic energy, not the actual value.

Once you have the final kinetic energy, you can calculate the change in kinetic energy using the equation:

ΔKE = final KE - initial KE

So, without information about John's mass, you won't be able to determine the change in kinetic energy.