A helicopter is ascending vertically. a passenger accidentally drops her wallet out the sides of the helicopter when it is 160 m above the ground. if the wallet hits the ground 7s later, at what speed was the helicopter ascending at the moment that the passenger let go of the wallet?

(A) 11.4 m/s
(B) 7.7 m/s
(C) 57.2 m/s
(D) 68.6 m/s
(E) 56.0 m/s

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.

In which of these cases are the two wave points considered to be in phase with each other?

The motion of water in a dam serves human beings by generating electricity as it is a controlled motion. give one example for an uncontrolled motion. what effects could it cause