Force and Work
What is force?
A push or pull on an object
W=f x d
What is kinetic energy?
The energy of motion
What two types of energy make up mechanical energy?
Kinetic energy and potential energy
State the law of conservation of energy
Energy cannot be created or destroyed
True of False: If an object does not move, work is done.
False
A force of 10 N moves an object 2 m. How much work is done?
20 J
What is the formula for kinetic energy?
KE = ½ x mass x speed²
What is the formula for mechanical energy?
Mechanical energy = Kinetic energy + potential energy
What happens to energy when it is conserved?
It changes form
What two factors are needed for work to be done?
Force and Distance
A woman lifts an object with a force of 85 N over 4 m. How much work is done?
340 J
Two objects move at the same speed. Which as more kinetic energy?
The object with more mass
An object has 40 J of KE and 15 J of PE. What is its mechanical energy?
What is power?
The rate at which work is done
Why is opening a stuck a jar an example of no work being done?
Because the jar does not move
A baby is lifted with 3.5 m with a force of 45 N. How much work is done?
A dog with a mass of 34 kg runs at 5 m/s. What is its kinetic energy?
425 J
A falling basketball has 30.8 J of KE and 16.0 J of PE. What is its mechanical energy?
46.8 J
How can you increase your power when stacking boxes?
Stack the boxes more quickly
Give or demonstrate an example of a force that does NOT do work.
Pushing on a wall, pushing an object that doesn't move.
If no distance is covered, how much work is done regardless of force?
0 J
Why does speed affect kinetic energy more than mass?
Because speed is squared in the formula
What factors determine an object's mechanical energy?
Motion, shape, position
Which has more power: doing the same work faster or slower? Why?
Faster, because power depends on time.