A 8 kg cat is running \( 4 \mathrm{~m} / \mathrm{s} \). How much kinetic energy does it have? A rolling ball has 18 joules of kinetic energy and is rolling \( 3 \mathrm{~m} / \mathrm{s} \). Find its mass.

To find the kinetic energy of the cat, we use the formula \( KE = \frac{1}{2} mv^2 \). Plugging in the values: \( m = 8 \, \text{kg} \) and \( v = 4 \, \text{m/s} \), we get \( KE = \frac{1}{2} \times 8 \times 4^2 = 64 \, \text{Joules} \). So, the cat has 64 Joules of kinetic energy! For the rolling ball, we rearrange the kinetic energy formula to find the mass: \( KE = \frac{1}{2} mv^2 \) means \( m = \frac{2 \times KE}{v^2} \). Plugging in the values: \( KE = 18 \, \text{J} \) and \( v = 3 \, \text{m/s} \), we get \( m = \frac{2 \times 18}{3^2} = 4 \, \text{kg} \). So, the mass of the ball is 4 kg!