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Questions and Answers
What is the formula for work?
What is the formula for work?
- Force x Distance (correct)
- Distance / Time
- Force + Distance
- Force / Distance
What is power?
What is power?
The rate at which work is done.
What is the SI unit of energy?
What is the SI unit of energy?
Joule
What is a watt?
What is a watt?
Work divided by time equals what?
Work divided by time equals what?
What is the unit of work?
What is the unit of work?
What is the unit of power?
What is the unit of power?
Force multiplied by distance equals what?
Force multiplied by distance equals what?
Work is done on an object when the object moves in the same direction in which the force is applied.
Work is done on an object when the object moves in the same direction in which the force is applied.
If you pull at an angle instead of in the direction in which the object moves, more of your force does work.
If you pull at an angle instead of in the direction in which the object moves, more of your force does work.
The farther you move an object, the more work you do.
The farther you move an object, the more work you do.
The more power you use to move an object, the more work you do.
The more power you use to move an object, the more work you do.
Power is the rate at which work is done.
Power is the rate at which work is done.
What is a machine?
What is a machine?
What is input force?
What is input force?
What is output force?
What is output force?
What is mechanical advantage?
What is mechanical advantage?
What is efficiency?
What is efficiency?
Machines are devices that allow you to _______________________ in an easier way.
Machines are devices that allow you to _______________________ in an easier way.
The force you exert when you use a machine is the _________________
The force you exert when you use a machine is the _________________
The force exerted by the machine is the _________________
The force exerted by the machine is the _________________
The force you exert on an object multiplied by the distance the object moves is equal to __________________, which is expressed in joules.
The force you exert on an object multiplied by the distance the object moves is equal to __________________, which is expressed in joules.
Divide output work by input work and multiply by 100% to find a machine's ______________
Divide output work by input work and multiply by 100% to find a machine's ______________
A machine's mechanical advantage is the output force multiplied by the input force.
A machine's mechanical advantage is the output force multiplied by the input force.
If the output force is greater than the input force, the mechanical advantage of the machine is greater than one.
If the output force is greater than the input force, the mechanical advantage of the machine is greater than one.
If the machine increases distance, the output force is greater than the input force.
If the machine increases distance, the output force is greater than the input force.
If a machine changes the direction but not the amount of the input force, the mechanical advantage is greater than 1.
If a machine changes the direction but not the amount of the input force, the mechanical advantage is greater than 1.
An ideal machine has no friction.
An ideal machine has no friction.
What is an inclined plane?
What is an inclined plane?
What is a wedge?
What is a wedge?
What is a screw?
What is a screw?
What is a lever?
What is a lever?
What is a fulcrum?
What is a fulcrum?
The ideal mechanical advantage of an inclined plane is the length of the plane divided by its force.
The ideal mechanical advantage of an inclined plane is the length of the plane divided by its force.
When you use a wedge, instead of moving an object along the inclined plane, you move the inclined plane itself.
When you use a wedge, instead of moving an object along the inclined plane, you move the inclined plane itself.
The thicker the wedge, the greater its mechanical advantage.
The thicker the wedge, the greater its mechanical advantage.
In a first-class lever, the fulcrum is between the input force and the output force.
In a first-class lever, the fulcrum is between the input force and the output force.
A knife is an example of a lever.
A knife is an example of a lever.
The lower arm acts like a first-class lever when it bends at the elbow.
The lower arm acts like a first-class lever when it bends at the elbow.
A flat sloped surface is called a(n) ____________________.
A flat sloped surface is called a(n) ____________________.
A device that is thick at one end and thin at the other end is a ____________________.
A device that is thick at one end and thin at the other end is a ____________________.
The threads of a screw act like a(n) ____________________.
The threads of a screw act like a(n) ____________________.
The fixed point that a lever pivots around is the ____________________.
The fixed point that a lever pivots around is the ____________________.
What is a pulley?
What is a pulley?
What is a wheel and axle?
What is a wheel and axle?
What is a compound machine?
What is a compound machine?
One of the simple machines that turns is the wheel and ______________.
One of the simple machines that turns is the wheel and ______________.
A single fixed pulley changes the ____________________ of a force.
A single fixed pulley changes the ____________________ of a force.
A system of fixed and _______________________ pulleys is called a block and tackle.
A system of fixed and _______________________ pulleys is called a block and tackle.
A screwdriver and a doorknob are examples of a(n) ______________________.
A screwdriver and a doorknob are examples of a(n) ______________________.
In a compound machine, the ___________________ of one simple machine becomes the input force of another simple machine.
In a compound machine, the ___________________ of one simple machine becomes the input force of another simple machine.
If a compound machine is made of a pulley with a mechanical advantage of 3 and a wheel and axle with a mechanical advantage of 5, the mechanical advantage of the compound machine is 8.
If a compound machine is made of a pulley with a mechanical advantage of 3 and a wheel and axle with a mechanical advantage of 5, the mechanical advantage of the compound machine is 8.
To find the mechanical advantage of a wheel and axle, multiply the radius of the wheel by the radius of the axle.
To find the mechanical advantage of a wheel and axle, multiply the radius of the wheel by the radius of the axle.
To find the mechanical advantage of a pulley, count the sections of rope that support the object.
To find the mechanical advantage of a pulley, count the sections of rope that support the object.
A bicycle is a compound machine because it contains more than one simple machine.
A bicycle is a compound machine because it contains more than one simple machine.
The part of a wheel and axle with the smaller radius is the wheel.
The part of a wheel and axle with the smaller radius is the wheel.
For work to be done on an object, ____________________.
For work to be done on an object, ____________________.
If you exert a force of 20 newtons to push a desk 10 meters, how much work do you do on the desk?
If you exert a force of 20 newtons to push a desk 10 meters, how much work do you do on the desk?
The mechanical advantage of a machine is the number of times a machine increases ____________________.
The mechanical advantage of a machine is the number of times a machine increases ____________________.
What is a simple machine that might be thought of as an inclined plane that moves?
What is a simple machine that might be thought of as an inclined plane that moves?
Give an example of a compound machine.
Give an example of a compound machine.
What is the ideal mechanical advantage for an inclined plane?
What is the ideal mechanical advantage for an inclined plane?
How can a hockey stick be considered a machine?
How can a hockey stick be considered a machine?
If tight scissors have an efficiency of 50 percent, what does that mean?
If tight scissors have an efficiency of 50 percent, what does that mean?
Power is measured in units called?
Power is measured in units called?
The wedge, screw, and lever are all?
The wedge, screw, and lever are all?
What is a screwdriver?
What is a screwdriver?
A device that is twice as powerful as another can do ___________________ the amount of work in the same amount of time.
A device that is twice as powerful as another can do ___________________ the amount of work in the same amount of time.
A machine makes work easier by multiplying force or __________________, or by changing direction.
A machine makes work easier by multiplying force or __________________, or by changing direction.
A ramp in a parking garage is an example of a simple machine called a(n)?
A ramp in a parking garage is an example of a simple machine called a(n)?
Power is equal to ______ divided by time.
Power is equal to ______ divided by time.
The force exerted by a machine is called the output force.
The force exerted by a machine is called the output force.
A wheel and axle is a compound machine.
A wheel and axle is a compound machine.
The ideal mechanical advantage of a wheel and axle is the radius of the wheel times the radius of the axle.
The ideal mechanical advantage of a wheel and axle is the radius of the wheel times the radius of the axle.
You do work on an object when you lift it off the floor onto a shelf.
You do work on an object when you lift it off the floor onto a shelf.
Joule is the rate at which work is done.
Joule is the rate at which work is done.
Is machine 1 classified as a simple or a compound machine?
Is machine 1 classified as a simple or a compound machine?
In machine 2, which letter represents the input force?
In machine 2, which letter represents the input force?
Which machines multiply the input force?
Which machines multiply the input force?
A bricklayer lifts a stack of bricks onto his shoulder, carries it across a room, and then lifts the bricks onto a ledge above his head. Explain if work is being done in each of these three situations.
A bricklayer lifts a stack of bricks onto his shoulder, carries it across a room, and then lifts the bricks onto a ledge above his head. Explain if work is being done in each of these three situations.
Explain how the ideal mechanical advantage and efficiency of a machine determine the machine's actual mechanical advantage.
Explain how the ideal mechanical advantage and efficiency of a machine determine the machine's actual mechanical advantage.
In what class of lever is the direction of the input force opposite to the direction of the output force?
In what class of lever is the direction of the input force opposite to the direction of the output force?
To which class of lever does each of the following machines belong: (i) fishing pole; (ii) wheelbarrow; (iii) bottle opener; (iv) pliers?
To which class of lever does each of the following machines belong: (i) fishing pole; (ii) wheelbarrow; (iii) bottle opener; (iv) pliers?
Explain why wedges and screws are actually types of inclined planes.
Explain why wedges and screws are actually types of inclined planes.
The output force of a lever with an ideal mechanical advantage of 3 is used as the input force of a pulley system with an ideal mechanical advantage of 2. What is the ideal mechanical advantage of the compound machine? Explain.
The output force of a lever with an ideal mechanical advantage of 3 is used as the input force of a pulley system with an ideal mechanical advantage of 2. What is the ideal mechanical advantage of the compound machine? Explain.
Why is it more difficult to steer a bike when your hands are close together on the handlebars than when they are far apart?
Why is it more difficult to steer a bike when your hands are close together on the handlebars than when they are far apart?
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Study Notes
Work and Energy
- Work is defined as force multiplied by distance; its unit of measurement is the joule (J).
- Power is the rate at which work is done and is measured in watts (W), where 1 watt equals 1 joule per second.
- The efficiency of a machine indicates the percentage of input work converted to output work.
Machines
- A machine is a device that makes work easier by increasing force, distance, or changing the direction of force.
- The force applied to a machine is called input force, while the force exerted by the machine is the output force.
- Mechanical advantage is the factor by which a machine increases the input force, calculated as output force divided by input force.
Types of Simple Machines
- Simple machines perform work with a single movement and include:
- Inclined Plane: A flat sloped surface that allows lifting objects more easily.
- Wedge: A device that tapers to a thin edge, facilitating splitting or lifting.
- Screw: An inclined plane wrapped around a cylinder.
- Lever: A rigid bar that moves around a fixed point known as the fulcrum.
- Pulley: A wheel with a groove that changes the direction of a force.
- Wheel and Axle: Comprises two circular objects that rotate together, aiding in movement.
Mechanical Advantage and Efficiency
- The ideal mechanical advantage for an inclined plane is its length divided by the height of the incline.
- In a compound machine, the output of one machine acts as the input for another, affecting overall efficiency.
- The effectiveness of a machine can be impacted by factors like friction, with an ideal machine having no friction.
Working with Forces
- Work is only done when an object moves in the same direction as the applied force, and this factor is crucial in calculating the work done on an object.
- If multiple forces are applied, only the component of the force in the direction of motion does work.
True or False Statements
- Work is done lifting an object if it moves; lifting is not the only condition to consider work done.
- The rate of doing work (power) does not equate to doing more work but rather doing work faster.
Class of Levers
- The configuration of forces in levers and their classes affect their functioning:
- First Class Lever: Fulcrum is between input and output forces (e.g., seesaw).
- Second Class Lever: Output force is between input force and fulcrum (e.g., wheelbarrow).
- Third Class Lever: Input force is between output force and fulcrum (e.g., fishing pole).
Practical Examples
- A bicycle is classified as a compound machine due to its multiple simple machines.
- A common application of a screw is its thread, acting as an inclined plane to convert rotational force to linear motion.
Working and Tools
- Household tools like screwdrivers are simple machines designed to ease tasks by amplifying applied forces or altering motion direction.
- Understanding the mechanics behind these machines allows for more efficient use in practical applications.
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