A 45 kilogram bicyclist on a 5 kilogram bicycle rides down a 50 meter high hill with her brakes partially on. Her speed at the bottom of the hill is 10 meters per second. How many kilojoules of heat were dissipated by the cyclist's brakes?

Q-1: A 45 kilogram bicyclist on a 5 kilogram bicycle rides down a 50 meter high hill with her brakes partially on. Her speed at the bottom of the hill is 10 meters per second. How many kilojoules of heat were dissipated by the cyclist's brakes?

ANSWER: 22.5 KILOJOULES or 22.0 KILOJOULES (based on 9.8 m/s2)

Q-2: A two-stage rocket attains a velocity of 3,000 meters per second when it drops the first stage and ignites the second. It consumes 1 kilogram of fuel per second and its exhaust speed is 2,000 meters per second. What is the thrust on the spacecraft?

1) 2,000 Newtons
2) 3,000 Newtons
3) 2,000 Newton-seconds
4) 3,000 Newton-seconds
ANSWER: 1 -- 2,000 NEWTONS

Q-3: A round viewing window with a 20 centimeter diameter is installed in a tank at the Shedd Aquarium. It is 5 meters below the water surface. The force on the window is approximately:

1) 1,500 Newtons
2) 10,000 Newtons
3) 25,000 Newtons
4) 50,000 Newtons
ANSWER: 1 -- 1,500 NEWTONS

Q-4:  The density of lead is 12 grams per cm3. A lead brick has a mass of 1.5 kilograms. Its dimensions are 10 cm by 5 cm by 4 cm. Is it:

1) More than 75% hollow
2) Between 50 and 75% hollow
3) Between 25 and 50% hollow
4) Between 0 and 25% hollow
ANSWER: 3 -- BETWEEN 25 AND 50% HOLLOW

Q-5:  Ice skating is possible and practical because of a unique property of water. Is it because:

1) The coefficient of kinetic friction of steel on frozen water decreases with decreasing Temperature
2) Ice readily sublimes
3) The melting point decreases with increasing pressure
4) Ice is a good thermal insulator
ANSWER: 3 -- THE MELTING POINT DECREASES WITH INCREASING PRESSURE

Q-6: 1 kilogram of boiling water is poured into an empty thermos whose mass is 1 kilogram and whose temperature is 25o Celsius. No heat is lost from the thermos. The specific heats of water and the thermos are 1 and 0.5 kilocalories per kilogram degree Celsius, respectively. Their final temperature is:

1) 50o Celsius
2) 65o Celsius
3) 75o Celsius
4) 90o Celsius (Read: "degrees Celsius")
ANSWER: 3 -- 75o CELSIUS

Q-7: An aluminum rod at a temperature of 100o Celsius radiates energy at a rate of 10 watts. If its temperature is increased to 200o Celsius, at approximately what rate will it radiate energy?

1) 15 watts
2) 20 watts
3) 26 watts
4) 80 watts
ANSWER: 3 -- 26 WATTS