Work and Machines Final Review
Nancy pushed a box with a force of 45 N for 15m Nancy pushed a box with a force of 45 N for 15m. How much work did Nancy do?
Answer 675J
The force that you apply to a machine is the?
Answer Input Force
When casting a fishing pole you need to apply 10N of force When casting a fishing pole you need to apply 10N of force. The pole in return will put out 30N of force. Calculate the mechanical advantage of the fishing pole?
Answer 30N/10N= 3
The mechanical advantage of a machine is the number of times a machine increases…
Answer The force exerted on the machines
What is the ideal mechanical advantage of an incline plane that is 6 What is the ideal mechanical advantage of an incline plane that is 6.0 m long and 1.5 m high?
Answer 6.0/1.5= 4.0
An ideal machine would have an efficiency of what?
Answer 100%
The ideal mechanical advantage for an inclined plane is equal to the length of the inclined plane divided by the what?
Answer Height
Pulling down on a rope to hoist a sail on a sailboat is an example of a machine that does what?
Answer Changes the direction over which a force is exerted.
The ideal mechanical advantage of a wheel and axle is equal to the…
Answer Radius of the wheel divided by radius of axle
If tight, rusty scissors have an efficiency of 50 %, half of your work is wasted do to what?
Answer Friction
What is the formula used to calculate the efficiency of a machine.
Answer Output work/inputwork x 100%
A ramp is an example of a simple machine called what?
Answer Inclined plane
Which of these is an example of a third-class lever?
Answer Your elbow
If the radius of a doorknob is 6 If the radius of a doorknob is 6.0 cm and the radius of its inner rob is 2.0 cm, what is the mechanical advantage?
Answer 6.0/2.0=3
A machine that utilizes two or more simple machines is called a what?
Answer Compound Machine
You do 5,000 J of work using a sledge hammer You do 5,000 J of work using a sledge hammer. The sledge hammer does 2,000J of work on the spike. What is the efficiency if the sledge hammer?
Answer 40%
One example of a compound machine is a?
Answer Bike, car, any thing that uses a variety of simple machines.
Which of the following describes a first class lever?
Answer -----------/\-------------- Fulcrum is in the middle
A(n)_________ is a grooved wheel with a rope, chain or cable running along the groove.
Answer Pulley
Which of the following simple machines is an inclined plan wrapped around a post?
Answer Screw
If you exert a force of 20 newtons to push a desk 10 m, how much work do you do on the desk?
Answer 200J
If a pulley is attached to something that doesn’t move, is called what?
Answer Fixed pulley
The fixed point that a lever pivots around is called the
Answer Fulcrum
A machine can do any of the following except…..
Answer Increase work
How does a ramp make it easier to move a heavy object a certain distance?
Answer It decreases the amount of force required to move the object.
When you raise or lower a flag on a flagpole, you are using a (n)
Answer Pulley
What do machines do?
Answer Change amount of force you exert or the distance over which you exert the force.
Which of the following equations should be used to calculate work done?
Answer W=FxD
Power is measured in units called
Answer Watts
The power of a light bulb that converts electrical energy at a rate of 100J per second is what?
Answer 100 Watts
______ is the rate at which work is done.
Answer Power
If you apply a force of 10N to a box and push it 10 m in 10 s, how much power did you deliver?
Answer 10 Watts
For work to be done on an object…
Answer Object must move in the same direction as the force applied
Which of these is an example of work being done on an object.
Answer Pushing an object across the room
Work is measured in what?
Answer Joules
If you exert a force of 15 N to push a desk 20 m, how much work do you do on the desk?
Answer 300J
________ is the rate at which work is done.
Answer Power