Lesson 3.4 - Conservation of Energy
VIDEO LESSON (18:15 min)
Video is not accessible in some countries. If you cannot view it, you might need VPN to do so.FIRST LAW OF THERMODYNAMICS
Energy cannot be created or destroyed. It can only change forms.
EXAMPLE PROBLEM #1
A skateboarder is travelling 4.2 m/s at the top of a 5.6 m ramp. What is his speed at the bottom of ramp?SOLUTION:
STATE DEPENDENT ANALYSIS
Notice that the analysis in the previous problem did not care about the path in which the skateboard travelled. The only information we needed was the initial and final states. The angle or shape of the ramp didn't matter.We can say this path independent.
Why will his speed not actually be the calculated value?
Some energy is transferred into heat via friction, air resistance, etc. Some energy is ALWAYS lost to system.
Due to the 1st Law of Thermodynamics that means that the final kinetic energy must be lower than the expected value and the skateboard will be travelling slower.
EXAMPLE PROBLEM #2
A Cannon fires a 3 kg cannon ball at \( 2.5 \times 10^2 \) m/s off a cliff. If the cannon ball is travelling at \( 3.0 \times 10^2 \) m/s when it hits the ground, determine the height of the cliff.SOLUTION:
END of LESSON
Modifié le: jeudi 19 mars 2026, 11:43