Physical Science in Applied Horizontal Force A worker pushes horizontally on a large crate with a force of 170 N, and the crate is moved 4.4 m. How much work was done?
While rearranging a dorm room, a student does 374 J of work in moving a desk 1.5 m. What was the magnitude of the applied horizontal force?
Physical Science in Applied Horizontal Force and the Kinetic Energy
What is the kinetic energy of a 15 kg dog that is running at a speed of 7.5 m/s (about 17 mi/h)?
How much work is required to lift a 2.90 kg object from the bottom of a well 8.7 m deep?
An object is dropped from a height of 15 m. At what height will its kinetic energy and its potential energy be equal?
A sled and rider with a combined weight of 64 kg are at rest on the top of a hill 21 m high.
(a) What is their total energy at the top of the hill?
J
(b) Assuming there is no friction, what would the total energy be on sliding halfway down the hill?
J
A man pushes a lawn mower on a level lawn with a force of 213 N. If 48% of this force is directed downward, and 51 W of power is expended in pushing the mower 4.6 m, how much time is spent in pushing the mower this distance?
A student who weighs 548 N climbs a stairway (vertical height of 2.6 m) in 30 s.
(a) How much work is done?
J
(b) What is the power output of the student?
W
A microwave oven has a power requirement of 1,253 W. A frozen dinner requires 7.0 min to heat on full power.
(a) How much electrical energy (in kWh) is used?
kWh
(b) If the cost of electricity is 10¢ per kWh, how much does it cost to heat the dinner? (Do not round your final answer. Fractional cent values are acceptable.)
¢
Work is done on an object when it is ___.
moved stationary acted on by a balanced force none of the preceding
What is the SI unit of energy?
watt ft·lb joule newton
Which of the following objects has the greatest kinetic energy?
an object with a mass of 4m and a velocity of v an object with a mass of 3m and a velocity of 2v an object with a mass of 2m and a velocity of 3v an object with a mass of m and a velocity of 4v
Physical Science in Applied Horizontal Force and Gravitational Potential Energy
The reference point for gravitational potential energy may be which of the following?
zero negative positive all of the preceding
When the height of an object is changed, the gravitational potential energy
increases decreases depends on the reference point remains constant
Mechanical energy is ___.
the same as total energy in all cases the sum of kinetic and potential energies always conserved all of the preceding
Power is expressed by which of the following units?
W·s N·m W/m J/s
What is required to do work?
Do all forces do work? Explain.
A weight lifter holds 900 N (about 200 lb) over his head. Is he doing work on the weights? Did he do any work on the weights? Explain.
If the speed of a moving object is tripled, how many times more work is required to bring it to rest?
Three times more work is required. There is no change in the work required to bring it to rest. Eighty-one times more work is required. Nine times more work is required. Twenty-seven times more work is required.
