writing prompt: 10/24/06 if you sit in my rolley chair and push off the wall with your feet, which...
TRANSCRIPT
Writing prompt: 10/24/06
If you sit in my rolley chair and push off the wall with your feet, which way will you move? Explain why this happens.
Force and Work
Newton’s Third
Work
We said before WORK and ENERGY are pretty much the SAME THING
Work is equal to the energy done
Work
So, if you raise a 10 kg mass up 1 meter in the air, the work you put into raising it, gives it its potential energy.
Potential Energy = m x g x h = 10 x 9.8 x 1
=98 Joules
That means your arm put 98 Joules of work into that mass
Work
QUESTION: How much work do the legs of a 50 kg person do to jump 1 meter in the air?
ANSWER: Work = Energy = m x g x h=50 x 9.8 x 1
=490 OR about 500 Joules
Work
Work is ALSO related to FORCE
Work is equal to the force used to move an object times the distance the object moved
Work = Force x distance OR W = F d
Work
W = F d
QUESTION: How much work is done to lift a 10 N box 2 meters?
ANSWER: W = F x d = 10 X 2 = 20 Joules(remember 1 Joule = 1 Nm “Newton meter”)
Work
W = F d
QUESTION: How much work is done if you push a box with 45 N for 3 meters?
ANSWER: W = F x d = 45 X 3 = 135 Joules(remember 1 Joule = 1 Nm “Newton meter”)
Newton’s 3rd law
Demo: book on a table, why doesn’t it fall?
Table pushes on the book with the SAME force that the book pushes on the table
Newton’s 3rd law
Newton’s 3rd law: Every action has an equal and opposite reaction.
OR
For every force applied to an object there is an equal force applied back in the other direction
Newton’s 3rd law
So if you get mad and PUNCH A WALL, it hurts YOU because the wall hits you with the same force you hit it with!!!!
Don’t punch walls…
Newton’s 3rd law
QUESTION: If you weight 500 N and you stand still on the ground, how much force does the ground push on you?
ANSWER: With the SAME FORCE, 500N
Newton’s 3rd law
QUESTION: If you punch a wall with 75 N of force, how hard does the wall hit you?
ANSWER: With the SAME FORCE, 75N
Newton’s 3rd law
QUESTION: If you punch a wall towards the right, what direction does the wall hit you?
ANSWER: in the OPPOSITE DIRECTION, to the LEFT!
Newton’s 3rd law
Let’s try an activity that incorporates work and force and Newton’s 3rd law
YAYYYYYY!!!!!!!!