Science Chapter 14: Mechanical Advantage Quiz

Questions and Answers

What is the IMA of a 120m long ski lift that carries skiers to a second station 40m above?

An inclined plane reduces the effort force by?

increasing the distance through which the force is applied

What is the ideal mechanical advantage of a pulley system equal to?

number of rope segments supporting the load

Why is the efficiency of a machine always less than 100 percent?

some of the energy is always lost to friction Signup and view all the answers

What is a wheel and axle?

simple machine Signup and view all the answers

What is the SI unit of power?

watt Signup and view all the answers

What is the AMA of a crowbar if you apply 40N of force to lift a 400N rock?

10 Signup and view all the answers

If you perform 40 joules of work lifting a 10N box, how high is the shelf?

4.0m Signup and view all the answers

How is the IMA of a wheel and axle found?

dividing the radius of the wheel by the radius of the axle Signup and view all the answers

When is a machine classified as a compound machine?

if it is made up of two or more simple machines Signup and view all the answers

What can you calculate if you know the input distance and output distance of a machine?

mechanical advantage Signup and view all the answers

Compare the actual mechanical advantage to the ideal mechanical advantage.

The actual mechanical advantage is less than the ideal mechanical advantage Signup and view all the answers

In which of the following is no work done?

None of the above Signup and view all the answers

Give an example of a compound machine.

bicycle, scissors Signup and view all the answers

How much work do you do if you exert a force of 10N to lift a box a distance of 0.9m?

9 Signup and view all the answers

How can a machine make work easier for you?

by changing the direction of your force Signup and view all the answers

What is the efficiency of a device that requires 420J of work to do 230J of work?

55% Signup and view all the answers

How much power do you use if you exert a force of 700N to walk 6m up a flight of stairs in 6 seconds?

700 watts Signup and view all the answers

What is the unit of work?

joule Signup and view all the answers

How many horsepower are 3730 watts?

5 horsepower Signup and view all the answers

What does the power of a machine measure?

its rate of doing work Signup and view all the answers

How can you make the work output of a machine greater than the work input?

increase mechanical advantage (reduce friction) Signup and view all the answers

What might a 750W motor also be rated as?

1 horsepower Signup and view all the answers

What kind of machine is an ax?

wedge Signup and view all the answers

What happens when you reduce friction in a machine?

increases its efficiency Signup and view all the answers

When does a force acting on an object do no work?

if the force is not in the direction of the object's motion Signup and view all the answers

To increase power, you can decrease the amount of work you do in a given amount of time.

False Signup and view all the answers

To increase power, you can increase the amount of work you do in a given amount of time.

True Signup and view all the answers

What amount of work must be supplied to a motor that has an efficiency of 75 percent to provide 240J of useful work?

320J Signup and view all the answers

When a machine does work, what can it do to force?

increase a force and increase the diameter a force moves an object Signup and view all the answers

What can a machine multiply?

force Signup and view all the answers

For work to be done on an object, what must happen to the object?

change its position Signup and view all the answers

The bottle opener is what class of lever?

second Signup and view all the answers

What does a machine change?

force Signup and view all the answers

The fulcrum is always between the effort force and the resistance force in a what kind of lever?

first Signup and view all the answers

Any part of a force that does not act in the direction of an object's motion does no what on an object?

work Signup and view all the answers

What do two or more simple machines working together make up?

compound machine Signup and view all the answers

What is the force that is exerted on a machine called?

input force Signup and view all the answers

What is the mechanical advantage of a machine?

the number of times that the machine increases the input force Signup and view all the answers

Which has the greater IMA?

A screw with closely spaced threads Signup and view all the answers

Why don't you do work as you hold a book motionless over your head?

there is no motion, so there is no work done Signup and view all the answers

Why is the work output of a machine never equal to the work input?

because some work input is lost to friction Signup and view all the answers

Which of these is NOT done by a machine?

Multiply energy Signup and view all the answers

A car stereo does 300J of work in 6s. How much power do you use?

50 W Signup and view all the answers

How much work is done if a dozen bagels weighing 11N are lifted a distance of 1.5m?

16.5 J Signup and view all the answers

If a human brain generates 20 watts of energy in 35 seconds, how much work is done?

700J Signup and view all the answers

What is the IMA of a pulley that can lift a 1185N weight with 395 N of exerted force?

3 Signup and view all the answers

Find the force a person exerts in pulling a wagon 20m if 2000J of work is done.

100N Signup and view all the answers

How could you increase the IMA of an inclined plane?

increase its length Signup and view all the answers

In which of the following situations do your arms do work on books?

Picking up a pile of books from the floor Signup and view all the answers

What is the IMA of a wheel and axle where the wheel has a radius of 10m and the axle has a radius of 2m?

5 Signup and view all the answers

What type of simple machine is your foot when you stand on your toes?

second class lever Signup and view all the answers

Study Notes

Ideal Mechanical Advantage (IMA)

A ski lift with a length of 120m and a height of 40m has an IMA of 3.
The IMA of a wheel and axle is calculated by dividing the radius of the wheel by the radius of the axle.
A pulley system's IMA equals the number of rope segments supporting the load.
A screw with closely spaced threads has a greater IMA compared to one with threads spaced farther apart.

Machines and Work

An inclined plane reduces effort by increasing the distance through which force is applied.
A compound machine consists of two or more simple machines working together.
No work is done if a force does not act in the direction of an object's motion, such as holding a book motionless.
A machine can make work easier by changing the direction of force or multiplying the force.

Efficiency and Power

Efficiency of a machine is calculated as (Output/Input) x 100%, with 100% efficiency being unachievable due to energy lost to friction.
A motor rated at 750W can also be described as 1 horsepower.
Power measures the rate of doing work, with the SI unit being the watt.
To increase power, either the amount of work done or the time taken must be adjusted.

Work Calculation

Work is calculated using the formula: Work = Force x Distance.
Lifting a box with a force of 10N over a height of 0.9m requires 9 joules of work.
A bag of bagels weighing 11N lifted 1.5m does 16.5J of work.
The work output cannot equal the work input due to friction losses.

Real-Life Applications and Examples

The actual mechanical advantage for a crowbar lifting a 400N rock with a 40N effort is 10.
A bicycle and scissors serve as examples of compound machines.
In everyday use, work done in lifting an object results in a change of position, thus confirming that work has been performed.

Levers and Forces

The fulcrum is located between the effort and resistance forces in a first-class lever.
The force applied to a machine is termed the input force.
Each part of a force that does not align with an object’s motion does not contribute to work.

Miscellaneous Facts

Energy generated by a human brain in 35 seconds equals 700J.
If you need to lift a crate using a motor with an efficiency of 75%, it must supply 320J to achieve 240J of useful work.
A second-class lever function is exemplified by standing on one's toes.
In carrying books, work is done when lifting them from the floor, but not when holding them stationary.

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Description

Test your understanding of mechanical advantage concepts in Science Chapter 14. This quiz covers topics such as ski lifts, inclined planes, and pulley systems. Prepare to explore how various machines function and calculate their efficiencies!