Simple Machines Pretest Flashcards
The output force for a machine is always less than work input because….
Some of the work done is used to overcome friction.
The unit for work is the…
Joule
What is power?
How fast work is being done.
The unit for power is the…
Watt
Name a situation where a person is doing work on an object.
A school crossing guard raises a stop sign that weighs 10 N.
Juan and Anita each lift an identical stack of books the same distance onto a table, but Anita does the job twice as fast. Therefore, her actions involve twice as much what?
Power
What does a fixed pulley change?
The direction of the force
When a machine increases the size of the force exerted, the distance through which the force is exerted….
Must decrease
What would increase the mechanical advantage of a first class lever?
Moving the fulcrum closer to the load
What is not an example of doing work according to the scientific definition?
Reading a chapter for homework
A man applies a force of 500 N to push a truck 10 m down the street. How much work has been done?
5000 J
What action does more work on an object?
Lifting a 90 N box 2 m off up the floor. ( look for a higher work value )
If you do 50 J of work in 5 seconds, your power is….
10 W
What is NOT a machine?
A glass
You apply 200 N to a machine and the machine applies 2000 N to an object. What is the mechanical advantage?
10
You apply 10 N to a machine and the machine applies 10 N to move another object. Since the input force is equal to the output force….
The mechanical advantage is 1.
Give an example of mechanical efficiency.
95% (any number less than 100 but not less than 0 in a precent form)
Getting regular oil changes for your car improves the car’s….
Mechanical efficiency
A ramp is an example of which simple machine?
Inclined plane m
Your muscles and bones form a what?
Lever
A jar lid is an example of a what?
Screw
What is an example of a wheel and axle?
Doorknob
What is the mechanical advantage of a wheel and axle where the wheel’s radius is 10 cm and the axle’s radius is 2 cm?
5
With a fixed pulley, the input force is….
Is always equal to the output force
A zipper is made of 3 what?
Wedges
When you turn a screw, you apply a….
A small input force over a long distance
What is NOT an example of doing work on a suitcase?
Carrying a heavy suitcase down a long hallway
If a machine has a work input of 8 N and gives a work output of 6 N, what is the machine’s mechanical efficiency?
75%
What is an example of a second class lever?
Wheelbarrow
In a second class lever….
The load is between the fulcrum and the input force
Hammering a nail into wood is an example of using a….
Third class lever
A movable pulley…
Is attached to the load
When a machine changes the size of a force, the ….. Must also change.
Distance
To do the same amount of work on an object, a large force is applied over a short distance can be exchanged by what?
Small force over a long distance
A single pulley changes the …. An object
Direction of the input force on
In 1994, a 3000 kg pancake was cooked, and flipped, in Manchester, England. Suppose you had a giant spatula that you could use as a lever to flip this pancake. Where could you best position the fulcrum and the pancake in order to get the greatest mechanical advantage?
Place the fulcrum close to the pancake as in a first class lever.
The largest turtle ever caught in the U. S. weighed about 844 N. How much work would be done to lift this turtle slowly 2 m from the surface of the water onto the deck of a research ship?
1688 J
What lever provides a mechanical advantage of less than 1?
Third class lever
What is the SI unit equivalent to 1 N times m?
Joule
What is the work you do on a machine such as turning a screwdriver called?
Work input
What is always less than 100% for a machine because of friction?
Mechanical efficiency
What is a block and tackle an example of?
Compound machine
What is done on an object when a force exerted on the object causes it to move in the direction of the force?
Work
What is also expressed as joules per second?
Watt
What is work done by a machine called?
Work output
What of a machine indicates how many times the machine multiplies force by comparing the input with the output force?
Mechanical advantage
What are machines consisting of 2 or more simple machines?
Compound machines
A pulley system in which a fixed and a movable pulley are used together
Block and tackle
What is a pulley attached to something that does NOT move?
Fixed pulley
When is work being done?
When you exert a force that moves an object in the direction of the force.
