Astone is thrown straight downward with a speed of 20 m/s from the top of a tall building. if the stone strikes the ground 3.0 seconds later, about how tall is the building?
a) 45m
b) 60m (wrong)
c) 90m
d) 105 m

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.

The ability to make things happen is also called a. heat b. force c. matter d. energy

How many electrons in an atom could have these sets of quantum numbers? =3n=3 electronselectrons =4,ℓ=2n=4,ℓ=2 electronselectrons =6,ℓ=ℓ=−1n=6,ℓ=2,mℓ=−1