Work
The metric unit for work
What is the joule?
The unit to measure power
What is the watt?
A machine that operates as a ramp and curves around a shaft ________
what is a screw
The fixed point around which levers rotate is called the _________
What is the fulcrum?
The measurement of how effective a machine is in using energy to do work is called:
Efficiency
The automobile jack exerts a force of 4,500 newtons to raise a car .25 meters. The amount of work done by the jack is how many joules?
what is 1,100 joules?
Running up a flight of stairs, Maria generates 450 watts of power. If it takes her 6 seconds to go up the stairs, the amount of work she does in running up the stairs is ___joules.
What is 2,700 joules
All of the following are simple machines, except:
scissors, bike, jackknife, and see-saw
a bike (a complex machine)
The mechanical advantage of a lever is the ratio of what?
the length of the input arm to the length of the output arm
Friction is the "catch-all" term for many processes that oppose ___________
motion
Is work accomplished when you stand still holding a large weight? Why or why not?
No. Work=FxD
An electrical water heater raises the temp of water by adding 8,000 joules of energy to the water in 40 seconds. The minimum power that must be supplied to the heater is ______ watts.
200 watts
what is the force directed along the ropes of a rope and pulley system called?
Tension
A simple machine will sometimes multiply your force or work?
Force.
2,000 joules
If there is an incline plane. A 60 N block at rest of the bottom is pushed up the incline. How much work is done? (length is 4.0 m, height is 3.0 m)
180 Joules
If one horsepower is equal to 746 watts, how much horsepower does a highly trained athlete generate by doing 350 joules of work per second?
0.469 horsepower
power = work
time = 350 joules
second = 350 watts
1 horsepower = 746 watts
power = 350 watts ×
1 horsepower
746 watts = 0.469 horsepower
The mechanical advantage is added in a pulley system by increasing the number of strands directly supporting the load. For instance, if two strands of rope support a 10 newton force, the tension of each rope is 5 newtons. What would the tension be on a three rope pulley system (two pulleys) supporting 15 N?
5 newtons
If the output force of a lever is greater than the input force, what does that mean about the input arm length vs. output arm length?
The length of the input arm is greater than the length of the output arm.
an incandescent light bulb uses 60 joules of electrical energy every second. Due to heat loss, the energy available for light is reduced to 6 joules per second. If this bulb is used to keep eggs warm in an incubator, how efficient is the light bulb at producing heat?
90 percent
If 60 joules of work are required to lift a 10 newton object 5.0 meters (on a pully), the amount of work done in overcoming friction as the weight is lifted is ____joules.
10 joules. (60-50=10)
Calculate the power required to move a 2,000-kilogram automobile to the top of a 100-meter hill in 15.0 seconds. Express the power both in units of watts and horsepower.
power = 130,667 watts = 175 horsepower
If a pulley system has 7 supporting ropes, a 140 lb boy can be lifted by what force? (in lbs)
20 lbs
Luis lifts a 500 newton load in a wheelbarrow 0.15 meters by raising the handles of a wheelbarrow 0.40 meters with a 200 newton force. The amount of work used to overcome friction is _______ joules.
Calculate input work= Fd= (200N)(1.4m)=80
output work=Fd=(500N)(0.15m)=75J
in a theoretical machine, how is work output calculated?
output work = fd= (output force)(output distance)