A cyclist has a mass of 64 kg and is travelling at a speed of 5.0 m/s. Calculate the kinetic energy of the cyclist in joules (J).

What you are being asked to find

You are given the cyclist’s mass and speed, and you need the kinetic energy, which is the energy of motion.

Choose the correct equation

Kinetic energy is calculated using:

$$E_k = \tfrac{1}{2}mv^2$$

where $m$ is mass in kg and $v$ is speed in m/s.

Substitute the values and calculate

Substitute $m = 64$ and $v = 5.0$:

$$E_k = \tfrac{1}{2}(64)(5.0)^2$$

Square the speed:

$$5.0^2 = 25$$

Now multiply:

$$E_k = 0.5 \times 64 \times 25 = 32 \times 25 = 800$$

Check the units

Using kg and m/s gives energy in joules, so the final answer is $800\,\text{J}$.