🟢 CONSERVATION OF ENERGY BASICS

Flashcard 1

Front: What does the Law of Conservation of Energy say?

Back: Energy cannot be created or destroyed. It can only be transformed from one form to another. The total mechanical energy (kinetic + potential) stays the same if no energy is lost (like from friction).

Flashcard 2

Front: What is mechanical energy?

Back: Mechanical energy is the total of kinetic energy (KE) and potential energy (PE).

Formula:

ME = KE + PE

Flashcard 3

Front: What is the formula for kinetic energy (KE)?

Back:

KE = ½ × m × v²

m = mass (kg), v = velocity (m/s)

Flashcard 4

Front: What is the formula for gravitational potential energy (PE)?

Back:

PE = m × g × h

m = mass (kg), g = 9.8 m/s², h = height (m)

Flashcard 5

Front: What is the formula for elastic potential energy (like in springs)?

Back:

PE_spring = ½ × k × x²

k = spring constant (N/m), x = compression/stretch (m)

Flashcard 6

Front: What is the spring constant (k)?

Back: A measure of how stiff a spring is. Higher k = stiffer spring. Units: N/m

Flashcard 7

Front: What is work?

Back:

Work = Force × Distance × cos(θ)

In energy problems, you can think of work as a way of transferring energy.

🟡 TIPS FOR ENERGY PROBLEMS

Flashcard 8

Front: When should you use KE = PE?

Back: When energy is transferred from motion to height or vice versa, and no energy is lost. Example: a car rolling up a ramp or falling down.

Flashcard 9

Front: What does “no energy losses” mean?

Back: It means we can ignore friction and air resistance. Total energy stays the same.

Flashcard 10

Front: How do you find how much energy is lost to heat or friction?

Back:

Energy lost = Initial energy - Final mechanical energy

Flashcard 11

Front: What is the relationship between energy and speed?

Back:

• More KE = higher speed.

• If you lose KE, your speed goes down.

• KE = ½mv² → to solve for v:
  v = √(2KE/m)

🔵 PROBLEM-SPECIFIC TOOLS

Flashcard 12

Front: What formula do I use when an object moves up a ramp and compresses a spring?

Back:

Initial KE + Initial PE = PE_spring

→ ½mv² + mgh = ½kx²

Flashcard 13

Front: What formula do I use when something falls onto a spring?

Back:

Start with just potential energy: PE = mgh

At max compression: PE_spring = ½kx²

So: mgh = ½kx²

Flashcard 14

Front: How do I find how fast something is moving just before hitting something?

Back: Use PE = KE

→ mgh = ½mv²

Solve for v:

v = √(2gh)

Flashcard 15

Front: How do I find the force of friction?

Back:

Work by friction = change in energy

W = F × d → So:

F = Energy lost / distance

Flashcard 16

Front: How do I handle “10% of energy lost” questions?

Back:

• Total energy × 90% = energy still available

• Then use that for KE or PE formulas.

🔴 THINGS TO MEMORIZE

Flashcard 17

Front: Value of gravity (g)?

Back: 9.8 m/s²

Flashcard 18

Front: What does “at rest” mean for KE?

Back: Velocity is 0, so KE = 0.

Flashcard 19

Front: How do you find “minimum work”?

Back: Work = change in energy (usually PE)

→ W = m × g × Δh

Flashcard 20

Front: What does it mean if something is compressed by a spring?

Back: The spring stores elastic potential energy:

PE_spring = ½kx²