How is one second time defined in SI system?

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground.what is his gravitational potential energy above the ground?

The electric potential a distance r from a small charge is proportional to what power of the distance from the charge? a. r^-1 b. r c. r^-2 d. r^2

To practice problem-solving strategy 10.1 for energy conservation problems. a sled is being held at rest on a slope that makes an angle θ with the horizontal. after the sled is released, it slides a distance d1 down the slope and then covers the distance d2 along the horizontal terrain before stopping. find the coefficient of kinetic friction μk between the sled and the ground, assuming that it is constant throughout the trip.