Work and Energy Flashcards
Work is given by the following equation ____.
Force * Distance = Work (Joules)
or
Force * Distance * Cos(theta)
Note that work is a measure of the energy that has been transferred by a force over a certain distance.
Work is a type of ______.
Energy
Energy is ______.
The ability to do work.
Work and energy share what unit?
Work and energy both have units of joules, or Nm (Newton meters).
Kinetic energy is given by the following equation: ______.
Kinetic energy = (1/2)mv2
Gravitational potential energy is given by the following equation ______.
Mass * Gravity * Height
Where the acceleration due to gravity is approximately 10m/s2
An object is dropped from a height of 10 meters. What kind of energy is the gravitational potential energy converted into?
The gravitational P.E. is converted into kinetic energy! Therefore, mgh = (1/2)mv2
What is the work done if the angle between the force and the displacement is 90 degrees?
This would mean that cosine(90) = 0, so no work is done!
The work energy principle states that the net work done on an object is equal to what?
Net work = K.E. Final - K.E. Initial
If the net work is positive, the object will speed up
If the net work is negative, the object will slow down
If the net work is zero, the object will maintain a constant speed as there is no change in the kinetic energy
What does it mean to do negative and positive work on an object?
Negative work = Force takes away energy from the object (e.g., friction)
Positive work = Force gives energy to the object
On a graph of force vs. position, what is the amount of work done equal to?
The work is equal to the area under the curve. This is true even if the force is chagning. This is helpful because we can only use the Work = Fd*cosine(theta) formula if the force being applied is constant!
If an object is sliding toward the right and the force of friction is acting in the opposite direction (i.e., to the left), what is the angle between the force and the displacement for the frictional force?
Because the frictional force is in the opposite direction of that the object is moving, the angle must be 180 degrees. Therefore, cos(180) = -1 and we get a negtive value for work done by friction!
