When you have completed the quiz, your score will appear here--->
Imagine that two students are given the task of raising a 10 kg brick 1.0 m. Student A lifts it straight up using her arms, and student B uses a well lubricated inclined plane. Which student will need to use less force and why?
Student B will need to use less force because the inclined plane offers a mechanical advantage
Student A will need to use less force because she does not encounter any friction
Student B will need to use less force because the inclined plane offers a speed advantage
Student A will need to use less force because she doesn't need to make the brick move as long a distance
A perpetual motion machine
would have 100% efficiency.
would have an output of less than 1.
is possible only in a vacuum.
cannot be stopped by gravity.
A machine that is efficient
can do useful work.
must have no energy lost to friction.
must be 100% to be effective.
must use more input force than an inefficient machine.
Which would not increase the efficiency of a bicycle?
Increase the number spokes in each wheel
Make the bicycle more streamlined
Lubricate the chain
Increase the air pressure in the tires
Which change made to a bicycle would affect its mechanical advantage?
Make the wheels larger in diameter
Increase the number spokes in each wheel
Lubricate the chain
Increase the air pressure in the tires
What is the difference between mechanical advantage and efficiency?
Efficiency is output work/input work and mechanical advantage is output force/input force
Mechanical advantage is output work/input work and efficiency is output force/input force
There is no difference, both are the same expression except that efficiency is expressed as a percentage and mechanical advantage is expressed as a number
As efficiency increases, mechanical advantage must decrease because friction is reduced
To increase the efficiency of a machine you must minimize what?
Friction
Gravity
Output work
Distance
Which statement about work and friction is true?
Friction does work by transforming input energy into heat
Friction is a force that does no work
Friction is a force that reduces the total work done by a machine
As the efficiency of a machine increases, friction must increase as well
A 60 N block is pushed up a 2 m long ramp. What is the efficiency of the ramp if 30 N of force is needed to raise the block 0.5 m?
50%
100%
75%
25%
Which statement about efficiency is false?
Efficiency can be calculated if you know the input force and the output force
The efficiency of a machine can be calculated if you know the input work and the output work
