Module 3 - Kinetic and Potential Energies Flashcards
What is the Kinetic energy equation
KE = 0.5mv²
What is meant by Kinetic energy
The work done due to the motion of an object with mass
Derive the KE equation
- W = KE = Fd
- F = ma
d = v² - u²/2a
assuming u = 0 then d = v²/2a - KE = ma x (v²/2a)
- KE = 0.5mv²
Describe the proportionalities for a constant speed and mass in relation to kinetic energy
- KE = km
- KE = kv²
What is the Work-Energy Principle
the work done by the net force on an object is equal to the change in kinetic energy of the object
What is meant by the gravitational potential energy of an object
The capacity to do work as a result of its position in a gravitational field
Derive the equation for GPE
W = GPE = Fd
F = mg, g = h
GPE = mgh
In what instances will the work be negative and why
- When the object is moving in the opposite direction to the line of action of the force, meaning that one of the displacement and the force will be negative
What is the relationship between the max GPE and max KE assuming no resistive forces
mgh = 0.5mv²
2gh = v²
v = sqrt(2gh)
Why is this only valid if we are assuming no resistive forces, include proportionality in explanation
- Resistive forces decrease the magnitude of the resultant force
- This will result in a lower acceleration
- This means ithat in the same time and distance a lower maximum velocity is reached
Proportionality:
s = vt -at²/2
v = (s+0.5at²)/t
Constants: t², t, 0.5, s
v = ka
Therefore if a decreases v does so too.
What is the equation for the conseration of mechanical energy
mgh₁ + 0.5mu² = mgh₂ + 0.5mv²
If there are resisistive forces, what will the the equation for the CoE be
mgh₁ + 0.5mu² + (work done by resistive forces) = mgh₂ + 0.5mv²
