Work Basics
What is the ability to do work
Energy
Power is defined as this quantity divided by time
work
This happens to power if the same amount of work takes longer to complete.
power decreases
A force of 10 N moves a box 2 m. This amount of work is done
20 Joules
Carrying a heavy backpack across the room at constant height results in this amount of work done on the backpack.
0 work
The formula used to calculate work
Work= Force x distance
What is the formula for power?
P= Work/time
A student lifts a box using the same amount of work but in half the time. This quantity increases.
power
A toy car is moving along with 0.40 joules of kinetic energy. If its speed is doubled, then its new kinetic energy will be
1.6 J
Lifting a box onto a shelf requires work because the force is in the same direction as this.
distance/motion
The unit used to measure work in the SI system.
Joule
What is the SI unit of power?
Watt
If you push on a wall and it does not move, this amount of work is done
no work
A force of 50 N moves an object 4 m. This amount of work is done
200 Joules
Two students lift identical boxes to the same height, but one lifts faster. This student has more of this.
power
1 Joule is equivalent to what?
1 Joule= Newton per meter
1Kg x m2s2 of N/m
1 Watt is equivalent to
Joules/sec
746 hp
This angle between force and motion results in zero work being done.
90 degrees
A machine does 500 J of work in 10 seconds. This is the power output
50 Watts
How would you calculate the total mechanical energy of a system?
PE+KE
Provide the formula for kinetic energy
KE= 1/2mv2
Provide the formula for either potential energy
PE= mgh
What does negative or positive work indicate?
energy being put into (positive) of taken out (negative) a system
Calculate the potential energy of a 5.2kg object positioned 8.5 meters above the ground
433.16 Joules
What is the Law of Conservation of Energy?
energy is neither created nor destroyed just transformed