## natasha.aries 2 years ago A 30 kg child and sled slides down a 9.0 meter high hill. It is going a speed 12 m/s at the bottom of the hill. How much mechanical energy was transformed into thermal energy? A 360 J B 490 J C 2160 J D 2646 J

1. cesckay

as the sleigh goes down, gravitational potential energy is converted to kinetic energy. hence if you find potential energy - kinetic energy, ur answer should be right about 490

2. natasha.aries

how do u know u subtract?

3. cesckay

Energy transferred( P.E) = work done ( K. E.) + heat energy.. potential energy is converted (transferred) to kinetic energy as the sleigh glides down the slope.. there must be some kind of friction opposing the motion but it is negligible i suppose. As it slides down, kinetic energy is increasing because its gaining velocity. hence the lossed energy is converted to heat since energy cannot be created or destroyed. Law of conservation of energy

4. natasha.aries

ohhh okay i think i get it lol

5. natasha.aries

thanks!

6. cesckay

:)