The drawing shows two boxes resting on frictionless ramps. one box is relatively light and sits on a steep ramp. the other box is heavier and rests on a ramp that is less steep. the boxes are released from rest at a and allowed to slide down the ramps. the two boxes have masses of 11 and 31 kg. if a and b are 5.0 and 1.5 m, respectively, above the ground, determine the speed of (a) the lighter box and (b) the heavier box when each reaches b. (c) what is the ratio of the kinetic energy of the heavier box to that of the lighter box at b?

In 1980, alfa romeo introduced the first system to smooth a rough idle caused by ignition and camshaft timing changes.

Acoal-fired plant generates 600 mw of electric power. the plant uses 4.8 x 10^6 kg of coal each day, and the heat of combustion of coal is 3.3x 10^7 j/kg. the steam that drives the turbines is at a temperature of 300° c, and the exhaust water is at 37° c. (a) what is the overall efficiency of the plant for generating electric power? (b) how much thermal energy is exhausted each day? (c) what is the change in entropy of the universe for this heat engine? (d) using the same heat reservoirs, what is the maximum possible (carnot) efficiency for a heat engine?

Suppose that 27 j of work is needed to stretch a spring from its natural length of 6 m to a length of 9 m. (a) how much work is needed to stretch the spring from 12 m to 14 m? j (b) how far beyond its natural length will a force of 78 n keep the spring stretched?