Chapter Seven: Work And Simple Machines

God’s Creation
what are some of the best simple machines based on?
the exchange of energy to create change in a physical system
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What is the SI unit for work?
-most familiar
-a force acts on an object, and it moves in the same direction as the force applied
-Example: if I push a toy car and it moves
mechanical work
1. an applied force
2. object has to move because of the force applied
2 Factors of mechanical work
w=fxd
(work equals force times displacement)
work formula
a vector
Is mechanical work a scalar or a vector?
the rate at which work is done
power
P=W/?t
(power = work divided by time interval)
what is the power formula?
watts
what is the unit for Power?
levers; wheel & axles; inclined planes
what can most simple machines be classified as?
false
True or false, simple machines create energy?
false
True or false, simple machines do more work than you put into them?
What you do. For example, if you swing a baseball bat.
What is the “effort force” of a simple machine?
What the machine does. For example, once a baseball bat is swung, the bat hits the ball and the ball goes flying.
What is the “resistance force” of a simple machine?
The system to be moved. For example, the ball that you hit in baseball.
What is the “load of resistance” of a simple machine?
To conserve work and energy, simple machines compensate for a smaller effort force by exerting that force over a longer distance. For example, when you hit the ball with a bat, it goes farther than if you swing your arm with all your might at the ball.
What is the distance principle?
A bar resting on a fulcrum
What is a lever?
Rotational Equilibrium
When a seesaw is balanced what stage is it in?
True, if the man is close to the fulcrum, and the kid is on the far other side, they can be balanced.
True/False, if a heavy person is on one side and a kid on the other side, the seesaw can be balanced
On the end of the lever
For a torque, where is the fulcrum?
First-Class lever
First-Class lever
Second-Class lever
Second-Class lever
Third-Class Lever
Third-Class Lever
2nd class
Which of the three levers is a force multiplier?
1st class
Which of the three levers is a direction changer?
3rd class
Which of the three levers is a distance multiplier?
3rd class
What kind of lever is a broom?
2nd & 3rd class
What kind of lever is a nail clipper?
Wheel- usually a disk that rotates around an axis
Axle- usually smaller disk that attaches to the wheel
Wheel and axle
Ferris wheel, car, bike
Wheel and axle examples
-modified wheel and axle
-if you move the smaller one, it is a distance multiplier
-if you move the bigger one, it is a force multiplier
Gears
A wheel with a groove on its edge mounted on an axle
Pulley
1. Single moveable
2. Single fixed
3. Pulley gangs
Types of pulleys
-ramps
-force multipliers
Inclined planes
-cut into things
-force multipliers
-examples include knives, door stops, and axes
Wedges
-long thin wedge wrapped around a spiral
-the more threads the easier to use
-force multipliers
Screws
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