Name _____ KEY ____________________________________ Date _________ Period ______
Power
1.
Two physics students, Eli and Peyton, are in the weightlifting room. Eli lifts the 100pound barbell over his head 10 times in one minute; Peyton lifts the 100-pound barbell
over his head 10 times in 10 seconds. Which student does the most work? Which student
delivers the most power? Explain your answers.
Each student does the same work, but Peyton delivers more power because he lifts
the weight in a shorter time period.
2.
A microwave does 1,500 joules of work in 30 seconds. What is the power of this
appliance?
3.
Emily’ vacuum cleaner ha a power ra ing of 200 watts. If the vacuum cleaner does
360,000 joules of work, how long did Emily spend vacuuming?
4.
A 1000-watt microwave oven takes 90 seconds to heat a bowl of soup. How many joules
of energy does it use?
W = P · t = (1000 W)(90 s) = 90,000 J
5.
One machine can perform 500 joules of work in 20 seconds. Another machine can
produce 200 joules of work in 5 seconds. Which machine is more powerful?
achine
achine
6.
A pile driver is a machine that lifts a heavy metal block upward and drops it to pound
support posts called piles into the ground so that bridges and buildings can be constructed
on them. A diesel engine can lift the 225 kg hammer of a pile driver 20. m in 5.0 s.
a. How much work is done on the hammer?
W = F · d = (mg)d = (225 kg x 9.8 m/s2)(20. m) = 44100 J
b. What is the power of the engine?
7.
Suppose a force of 130 N is used to push an object a distance of 5.2 meters in 15 seconds.
Find the work done and the power for this situation.
W = F · d = = (130 N)(5.2 m) = 676 J