An electric crane lifts a load of bricks and transfers 90 kJ of gravitational potential energy to them. The crane has an efficiency of 0.8. Calculate the amount of energy transferred to the crane by electricity.

Using the free-body diagram, calculate the net force acting on the sled. is the sled in a state of dynamic equilibrium?

Why do atoms emit energy of only specific wavelengths

A980-kg sports car collides into the rear end of a 2300-kg suv stopped at a red light. the bumpers lock, the brakes are locked, and the two cars skid forward 2.6m before stopping.the police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact. what was that speed?