Question

825 KG child is using a one KG skateboard to travel down the hill. If the child has 165J of kinetic energy after traveling down the hill what is the child’s speed in meters per second?

Answer 1

KE= 0.5mv^2

165J= 0.5×(825kg+1kg)×v^2

165J = 413kg×v^2

v^2=165J÷413kg

v^2=0.39952 m^2/s^2 (5s.f.)

v= √0.39952= 0.632 m/s (3.s.f.)

Answer 2

That poor child weighs 1,818 pounds !  He can't stand up, can't hold himself upright on a skateboard, has probably been banned from every hill in town, and no 1-kg skateboard can hold all of him.

This must be a big part of the reason why his speed down the hill is only 0.632 meter/second . . . about 1.4 miles per hour.

You can WALK at east twice that fast.