Work and Power
Work and Power
Machines
Simple Machines
Word problems
100
The SI unit of power
Watt
100
For a force to do work on an object, some of the force must act in the same____________as the object moves.
direction
100
Machines make work_______to do
easier
100
A simple machine that consists of two disks or cylinders, each with a different radius
Wheel and axle
100
A large semi-truck is moving a house from one lot to another. The amount of force required to move the house horizontally a distance of 67.2 meters is 3,400 newtons. How much work will be done on the house?
w = f x d
w = 3400 N x 67.2 m
w = 228480 J
200
The product of force and distance
Work
200
Any part of a ____________that does not act in the direction of motion does no work on a object.
force
200
the force you exert to make the machine work
Effort force
200
A v-shaped object whose sides are two inclined planes sloped towards each other
Wedge
200
Children are sled riding on a hill. One little girl pulls her sled back up the hill and does 377 joules of work while pulling it back up the 15.3 meter hill. If she does this in 53 seconds, what is her power output?
p = W / t
p = 377 j / 53 s
P = 7.11 watts
300
The rate of doing work
Power
300
If there is no__________________no work is done.
movement
300
Units for Mechanical Advantage
None
300
A rigid bar that is free to move around a fixed point
Lever
300
Suppose the box weighs 90 N. If the mechanical advantage of this pulley system is 2, what is the force needed to lift the box?
MA = FR / FE
2 = 90 N / FE
FE = 90 N /2
= 45 N
400
The SI unit of work
Joule
400
Formula for calculating work
work=force X distance
400
As the angle of the inclined plane increases, what happens to the force and distance
the force required to raise the object increases and the force must be applied over a smaller distance
400
A simple machine that consists of a rope that fits into a groove in a wheel
Pulley
400
What is the mechanical advantage of the following ramp?
MA = DE / DR
MA = 50 m / 25 m
MA = 2
500
Is equal to about 746 watts
Horsepower
500
When using SI units in the work formula, force is in _________and distance is in ____________
newtons
meters
500
How do you calculate the mechanical advantage of a wheel and axle
MA = Radius of Wheel / Radius of Axle
500
An inclined plane wrapped around a cylinder
Screw
500
A weightlifter presses a 400 N weight 0.5 m over his head in just 2 seconds. What is the power of the weightlifter?
W = F x d
W = 400 N x .5 m = 200 J
P = w / t
P = 200 J / 2 sec = 100 watts