The formula for kinetic energy is KE = 1/2mv^2, where m = mass, v = velocity
Plug your numbers into the formula
KE = 1/2(70kg)(9m/s)^2
KE=35kg(81m^2/s^2)
KE= 2835 J
This is the answer if you don’t need to use significant figures (if you’ve never heard of those then ignore work below and your answer is 2835J)
If you need to use significant figures, I’ll show that work below
KE = 1/2(70kg)(9m/s)^2
KE=(40kg)(80m^2/s^2)
KE = 3000 J
Remember when multiply SFs, your answer can only contain the amount of SFs as the number with the lowest amount of SFs
