Machine?
What is a machine?
A device that makes work easier.
How do you find mechanical advantage?
This is calculated using the actual forces measured (Output Force divided by Input Force)
MA= Fout/Fin
What is the number that tells you how many times a machine multiplies force?
Mechanical Advantage
What is the mechanical advantage if you use 70N to make a machine exert 245N?
MA= Fout/Fin
= 245N/70N
= 3.5
The result when a force moves an object a certain distance
Work
What are the three ways a machine can make work easier?
Provide an example for each Bonus (300 points)
1. Increasing the force applied. (e.g. carjack or nutcracker)
2. Changing the direction of the force. (e.g. elevator or pully for the blinds)
3. Increasing the distance over which force is applied (e.g. a ramp or staircase)
Which is better, a machine with a mechanical advantage of 3 or 8?
8
Remember, the mechanical advantage tells you how many times a machines multiplies your input force.
A group of parts that work together to perform a specific task.
A system
What is the output force of a machine with a mechanical advantage of 5, if you use 45N of force?
5 = ?/45n
5 x 45N = ?
= 225N
The ratio of output force to input force
Mechanical Advantage
What are three examples of machines?
Scissors, knife, screwdriver, pencil sharpener, car,...
If you push with 20N to move a 300N desk up a ramp, what is the mechanical advantage of the ramp?
300N/20N = 15
A group of physical parts that work together to perform a specific task.
Provide an example (Bonus 100 points)
Physical System
Computer or solar system
What is the formula for work?
Suppose Jomi pushes a box with a force of 150N and moves it 5 m. How much does the box move?
W=Fd
= 150N x 5m
=750 J
What is the metric unit for force?
Who is it named after and why? (Bonus 200 points)
Newton (N)
Since weight is the force of gravity, it is named after Sir Issac Newton
True or False:
Machines increase the amount of work done
False
In real life, because of friction and other energy loses, the work output is actually a little less than the work input. Machines do make the work easier.
What are the units of measure for mechanical advantage?
There are no units
A group of people who join together to accomplish certain tasks.
Provide an Example (Bonus 100 points)
Social System
School system or ant colony
Machine A uses 40N of force when you push with 30N. Machine B uses 50N of force when you push with 40N. Which machine has a better mechanical advantage?
Machine A has a better mechanical advantage of 40/30 = 1.33
While Machine B = 50/40 = 1.25
___________ is the force that opposes the relative motion of an object.
Provide an example.
Friction
Rubbing your hands together creates thermal energy because it is resisting the force
Why does using a longer ramp make lifting a load easier, even though the work does not change?
The input force is spread out over a longer distance
What does it mean if the mechanical advantage is less than one?
Provide an Example (Bonus 100 points)
The output force is less than the input force, but it increases the speed and range of motion of the output compared to the input
For example, a hockey stick hitting a puck
MA > 1 Machine multiplies the force
MA = 1 Machines only changes direction
MA < 1 Machines multiples distance/speed instead of force
What are the two types of force? Provide an Example of each.
Contact Force - kicking a soccer ball
Action at a distance - gravity pulls an object to the ground
What is the formula for Force of gravity?
What is the weight of a 50 kg student on Earth?
Fg = mg
= (50 kg)(9.8 N/kg)
= 490 N
Therefore a 50 kg student weighs 490 N on Earth
What are the 2 categories of energy?
Provide an example for each.
Kinetic energy - is when the object is in motion (moving car)
Potential energy - when energy is stored in an object (stretching a rubber band)