Science F & E Chapter 3 Lesson 2
The efficiency of an actual machine is always less than ...................... %
100
An ideal machine would have an efficiency of ......................
100 percent
Machines are devices that allow you to do ...................... in an easier way.
work
The force exerted on an object multiplied by the distance the object moves is equal to ......................, which is expressed in joules.
work
What causes a mechanical advantage that is greater than 1?
when the output force is greater than the input force
What causes a mechanical advantage that is less than 1?
when the output force is less than the input force
When you raise or lower a flag on a flagpole, you are using a(n) ......................
pulley
Without friction there would be
equal input and output work
If a machine changes the direction, but not the amount of the input force, the mechanical advantage is ...................... 1
equal to
A machines's ...................... is the number of times a machine increases a force exerted on it.
mechanical advantage
What is the formula for calculating mechanical advantage?
mechanical advantage = output force divided by input force
Your ...................... work can never be greater than your ...................... work.
output ........... input
The force exerted by the machine is the .......................
output force
The mechanical advantage of a machine that changes only the direction of force is ......................
1
The output work of a certain machine is 12,600 J. If the input work is 18,000 J, the efficiency is ......................
70%
What is the formula for calculating efficiency?
Efficiency = output work divided by input work times 100%
Machines just ...................... the way you do work.
change
Pulling down on a rope to hoist a sail on a sailboat is an example of a machine ......................
changing the direction over which the force is exerted
A machine makes work easier by multiplying force or ......................, or by changing direction.
distance
A machine's mechanical advantage is the output force ...................... by the input force.
divided
Machines (do/do not) reduce the amount of work you do.
do not
Divide output work by input work and multiply by 100% to find a machine's ......................
efficiency
Machines make work easier by changing ......................
force, distance, or direction
All machines waste some work overcoming the force of ......................
friction
An ideal machine has no ......................
friction
If tight scissors have an efficiency of 50 percent, half of your work is wasted due to ......................
friction
Since all machines lose work to ......................, ideal machines do not exist.
friction
The ideal mechanical advantage would equal the actual mechanical advantage if there were no losses due to ......................
friction
If the output force is greater than the input force, the mechanical advantage of a machines is ...................... 1.
greater than
The force applied to a machine is called the ...................... force.
input
The force you exert when you use a machine is the .......................
input force
What happens to the efficiency of a bicycle as it gets rusty?
it decreases
All machines have an efficiency of ...................... 100 percent.
less than
If a machine increases distance, the output force is ...................... the input force.
less than
If the output force is less than the input force, the mechanical advantage of a machine is ...................... 1.
less than
...................... are devices that allow you to work in an easier way.
machines
The mechanical advantage of a machine is the number of times a machine increases .......................
the force exerted on a machine
