Download Work and Machines - Powers Physical Science

Work and Machines
Final Review
• 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. 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 6.0 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 thirdclass lever?
Answer
• Your elbow
• 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. 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