Find the KE of a 60-kg runner who covers 400 m in 45s at constant speed.
To find the kinetic energy (KE) of the runner, we need to use the formula:
KE = 1/2 * m * v^2
Where:
- KE is the kinetic energy
- m is the mass of the object (runner) in kilograms
- v is the velocity of the object in meters per second
In this case, we are given the mass of the runner (m = 60 kg) and the distance covered (d = 400 m) along with the time taken to cover that distance (t = 45 s).
First, we need to calculate the velocity of the runner. Velocity is defined as the displacement divided by the time taken:
v = d / t
Substituting the given values, we have:
v = 400 m / 45 s
v = 8.89 m/s (rounded to two decimal places)
Now that we have the velocity, we can calculate the kinetic energy using the formula mentioned above:
KE = 1/2 * m * v^2
KE = 1/2 * 60 kg * (8.89 m/s)^2
Calculating further:
KE = 1/2 * 60 kg * 79.06 m^2/s^2
KE = 2381.8 Joules (rounded to one decimal place)
Therefore, the kinetic energy of the runner is approximately 2381.8 Joules.