Studied by 0 peopleA boy pushes on a parked car with a force of 200 N, The car does not move. How much work does the boy do on the car?
C. Zero
What are the units of work?
C. All of the above
Which of the following processes requires the most work?
c. A person lifts a 1 kg weight I m off the floor.
c. A person lifts a 1 kg weight I m off the floor.
d. All of the above
A weightlifter presses a 400 N weight 0.5 m over his head in 2 seconds, What is the power of the
weightlifter?
D. 100 watts
A machine is a device that
D. can multiply and change the direction of an input force
A wheelbarrow is an example of a
b. second-class lever.
Which of the following is an example of a third-class lever?
b. a hand-held boat paddle
Which of the following is not a simple machine?
b. a pair of scissors
What is the mechanical advantage of a single fixed pulley?
A. 1
Which of the following is not in the inclined plane family?
D. a wheel and axle.
What is the gravitational potential energy of a 55 kg box that is 8.0 m above the ground?
c. 4300 J
Gravitational potential energy depends on the
d. All of the above
A medicine ball has a mass of 5 kg and is thrown with a speed of 2 m/s. What is its kinetic energy?
b. 10 J
Which of the following is an example of mechanical energy?
c. potential energy
The kind of energy associated with atomic bonds is
C. chemical energy
Which of the following statements is not true?
c. If the kinetic energy of an object decreases, the nonmechanical energy will decrease.
The efficiency of a ramp is 75%. If the amount of work input is 240 J, what is the amount of useful work output?
D. 180 J
An object weighing 75 N is dropped from the top of a building and falls a distance of 28 m to the ground. How much work does gravity do on the object from the time it is dropped to the time it hits the ground?
C. 2100 J
An object has a kinetic energy of 810 J after falling a certain distance. If the mass of the object is 20 kg, what is the speed of the object at this time?
B. 9 m/s
The law of conservation of energy states that
D. energy can neither be created nor destroyed.
In which of the following is no work done?
D. none of the above.
A force acting on an object does no work if
b. the force is not in the direction of the object's motion.
What is the unit of work?
A/B: Joules and Newton/Meter
If you exert a force of 10.0 N to lift a box a distance of 0.9 m, how much work do you do?
B. 9.0 J
If you perform 40 joules of work lifting a 10-N box from the floor to a shelf, how high is the shelf?
C. 4.0 m
Which of the following statements is true?
C. To increase power, you can increase the amount of work you do in a given amount of time, or you can do a given amount of work in less time.
3730 watts equals about how many horsepower?
A. 5
A machine is a device that can multiply
A. Force.
When a machine does work, it cannot do which of the following?
D. increase a force and increase the distance a force moves an object.
How can a machine make work easier for you?
B. by changing the direction of your force
A 120-m long ski lift carries skiers from a station at the foot of a slope to a second station 40 m above. What is the IMA of the lift?
B. 3
The efficiency of a machine is always less than 100 percent because
b. some work input is lost to friction.
An ax is an example of a(an)
C. Wedge
The ideal mechanical advantage of a pulley system is equal to the
C. number of rope segments supporting the load.
The ideal mechanical advantage of a wheel and axle is found by
B. by dividing the radius of the wheel by the radius of the axle.
An example of a compound machine is a
B. bicycle
A machine is classified as a compound machine if it
c. is made up of two or more simple machines that operate together.
Work is a transfer of
c. Mass.
A small 20-kilogram canoe is floating downriver at a speed of 2 m/s. What is the canoe's kinetic energy?
B. 40 J
An object's gravitational potential energy is NOT directly related to which of the following?
c. its speed
The gravitational potential energy of an object is always measured relative to the
c. reference level from which the height is measured.
Which of the following increases when an object becomes warmer?
d. thermal energy
The energy stored in gasoline is
a. chemical energy.
Walking converts what type of energy into mechanical energy?
a. chemical energy
The equation E=mc2 relates energy and
C. mass
What is biomass energy?
A. the chemical energy stored in living things
Fossil fuels currently account for the majority of the world's energy use because they are
c. relatively inexpensive and readily available.
A benefit of a hydrogen fuel cell is that its byproduct is
c. water.
Based on your knowledge of energy conservation, which of the following statements is true?
both a and b
The formula for calculating kinetic energy can be written as
Ke= 1/2 mv^2
The energy of a moving object due to its motion is called
Kinetic Energy
The source of the energy when dynamite explodes is
Chemical energy.
A(n) ________ exchanges energy with the outside.
Open System
You calculate work by multiplying the force acting in the direction of ________ by the distance the object moves.
motion
Besides a reduction in friction, the only way to increase the amount of work output ofa machine is to _______________ the work input.
increase
The mechanical efficiency of any machine is always ______ than 100 percent.
less
As the thickness of a wedge of given length increases, its IMA
decreases
Energy resources that exist in limited amounts and, once used, cannot be replaced except over the course of millions of years are called _______ energy resources.
nonrenewable.
A worker uses a cart to move a load of bricks weighing 680 N a distance of 10 m across a parking lot. If he pushes the cart with a constant force of 209 N, what amount of work does he do? Show your work.
2090 Joules
The input force of a pulley system must move 8.0 m to lift a 3000-N engine a distance of 2.0 m. What is the IMA of the system? Show your work.
IMA= 4
A force of 1 1 N is applied to the handle of a screwdriver being used to pry off the lid of a paint can. As the input force moves through a distance 0.3 m, the screwdriver does 3 J of work on the lid. What is the
efficiency of the screwdriver? Show your work.
91% effciency
What is the kinetic energy of a 72.0-kg sky diver falling at a terminal velocity of 79.0 m/s? Show your work.
224,676 J
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