NAME __________________________________________________ DATE ___________________
Skills Worksheet
Math Skills
Power
Power equation:
1. Suppose you have a horse that has a power output of 750 W. How much work does this horse do in
0.55 s?
2. A ship’s diesel engine has a power output of 13.0 W (13.0  106 W). How much work is done by
this engine in 15.0 min?
3. Lithuania’s major nuclear power plant has one of the world’s most powerful generators, which
has a power output of 1.45  109 W. How long must this generator run if it is to provide the
energy to do 4.35  1011 J of work?
Work
Work equation:
1. You must exert a force of 4.5 N on a book to slide it across a table. If you do 2.7 J of work in the
process, how far have you moved the book?
2. A child pulls a sled up a snow-covered hill. In the process, the child does 405 J of work on the
sled. If she walks a distance of 15 m up the hill, how large a force does she exert on the sled?
3. An old house is being lifted by a type of crane from its foundation and moved by truck to another
location. After the house has been set on the truck bed, the truck accelerates until it reaches a
constant speed. If the force required to move the house horizontally a distance of 75.5 m is 3,150 N,
how much work has been done on the house?
Gravitational Potential Energy
Gravitational potential energy equation:
1. The world record for pole vaulting is 6.15 m. If the pole vaulter’s gravitational potential is 4,942
J, what is his mass?
2. In 1993, Cuban athlete Javier Sotomayor set the world record for the high jump. The
gravitational potential energy associated with Sotomayor’s jump was 1,970 J. Sotomayor’s mass
was 82.0 kg. How high did Sotomayor jump?
3. With an elevation of 5,334 m above sea level, the village of Aucanquilca, Chile is the highest
inhabited town in the world. What would be the gravitational potential energy associated with a
64 kg person in Aucanquilca?
Kinetic Energy
Kinetic energy equation:
1. The kinetic energy of a golf ball is measured to be 143.3 J. If the golf ball has a mass of about 47
g, what is its speed?
2. The most massive Shinkansen bullet trains are the series-200 trains. This type of train also has
one of the highest operating speeds: 76.4 m/s. If a series-200 train has a maximum kinetic energy
of 2.78  109 J, what is its mass?
3. A cheetah can run briefly with a speed of 31 m/s. Suppose a cheetah with a mass of 47 kg runs at
this speed. What is the cheetah’s kinetic energy?
Efficiency
Efficiency equation:
1. The resistance of water to an oar in a rowboat limits the oar’s efficiency to 0.450. If the rower
does 145 J of work on the oar with each stroke, how much useful work is done by the oar?
2. An automobile gasoline engine is able to do 225 J of useful work with each stroke of its pistons.
If the engine has an efficiency of 29.0 percent, what is the amount of work that must be done on
the pistons in the engine?
3. A forklift developed in Sweden is able to do 1.8  106 J of useful work in lifting a heavy load.
Suppose 7.6  106 J must be done by the lift’s motors on the load in order to accomplish this
task. What is the efficiency of the forklift?