Velocity of a Hot-Air Balloon A hot-air balloon rises vertically from the ground so that its height after t sec is given by the following function. h=1/2t2+1/2t
(a) What is the height of the balloon at the end of 40 sec?
(b) What is the average velocity of the balloon between t = 0 and t = 30?
ft/sec
(c) What is the velocity of the balloon at the end of 30 sec?
ft/sec

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?

Aball is thrown upward. at a height of 10 meters above the ground, the ball has a potential energy of 50 joules (with the potential energy equal to zero at ground level) and is moving upward with a kinetic energy of 50 joules. what is the maximum height h reached by the ball? consider air friction to be negligible. 1. h ≈ 10 m 2. h ≈ 50 m 3. h ≈ 30 m 4. h ≈ 40 m 5. h ≈ 20 m 003 10.0 points which of the two object shown below has the greatest kinetic energy? a m b 1 2 m v 2v 1. kinetic energies are the same. 2. a 3. b 4. unable to determine. 004 10.0 points tim, with mass 74.6 kg, climbs a gymnasium rope a distance of 3.1 m. the acceleration of gravity is 9.8 m/s 2 . how much potential energy does tim gain? answer in units of j. 005 10.0 points a car is moving at 64 miles per hour. the kinetic energy of that car is 5 × 105 j. how much energy does the same car have when it moves at 111 miles per hour? answer in units of j. 006 10.0 points an 102 kg man climbs up a 1 m high flight of stairs. the acceleration of gravity is 9.81 m/s 2 . w

Astone is dropped from a cliff and falls 9.44 meters. what is the speed of the stone when it reaches the ground? a. 13.6 m/sec b. 1.39 m/sec c. 185 m/sec d. 9.80 m/sec