Work
Power
Simple Machines
Forces
Laws of Motion
100
The units for work
Joules (J)
100
The units for power
Watts (W)
100
Simple machines cannot change the amount of ______________________
Work!
100
A car is stopped at a red light. It has a weight of 2000N. What is the net force on the car?
0 N. The net force must be zero if the car is not changing its motion.
100
The law of Inertia is the _______ Law
1st
200
W= Fxd
If Ian was to push a 50 N box for a total distance of 3m, how much work was accomplished? (Units too)
50 x 3 = 150 J
200
You competed against your friend in a power competition, and won. You both did the same task, so which of the following must be true?
-You did more work than your friend
-You did the task in less time than your friend
-Your friend did less work than you
-Your friend did the task faster than you
If same task, then same work=
-You did the task in less time than your friend
200
A simple machine can never be perfect because there will always be energy lost to __________________
Friction / Heat / Thermal energy
200
Which force has to be larger in order to get the car to start moving forward?
Driving force > resistive force
200
F = ma is the ____________ law
2nd
300
In order for word to be done, describe in words what must have happened.
A force needed to move something in the same direction as the force
300
P = W/t
If Jeremy pulls a car weighing 300N a distance of 20m in 6 seconds for 6000J of work, what was his power?
6000J/6s= 1000 W
300
Simple machine that uses a moving intersection of 2 inclined planes in order to split things easily by multiplying the input force.
A wedge
300
Unbalanced forces mean which of the following?
-That the object must speed up
-That the object must slow down
-That the object must change its motion
-That the object must change its motion
300
Action-Reaction is the _________ law
3rd
400
W= Fxd, F= W/d , d= W/F
If a 30N weight box is pushed until 90J of work was accomplished, how far was it pushed?
d= W/F
90J/30N = 3 m
400
P= W/t
When you do the dishes you might do 2 J of work in 30 minutes. How powerful are you?
2/30= .06 W (6 repeating)
400
This simple machine allows you to change the magnitude of an input force depending on the size of the wheel you turn and the accompanying spin of the turning post that results.
Wheel & Axle
400
When skydiving, gravity will continue to accelerate you down. At some point, you will achieve terminal velocity, when the air resistance pushing up exactly matches your weight pulling you down. What happens then?
Net force of 0 N means your motion will not change / will stay the same (falling fast but no faster)
400
When you jump up, you actually push the Earth down. Which law of motion fits best?
3rd Law
500
With which of the following is no work done:
-Holding a cup above your head
-Throwing a ball
-Lifting a pen
-Swimming
Holding a cup above your head
(no motion = no work)
500
Throwing a football with 100 N of force across a distance of 50m in 20 seconds would produce how much power?
W= F x d, P = W /t
P = 100 N x 50m / 20s = 250W
500
Why do we use simple machines?
To make work easier
500
Define mass, and weight, and say which is different for you on Jupipter compared to Earth
Mass - amount of matter
Weight - amount of force pulling you due to gravity
Mass is the same anywhere you go
500
A small car can accelerate on the highway faster than a large semi-truck. Which law explains this?
The 2nd Law