Feynman’s Lectures Exercises 2.14 and 2.15
If the weights and move the distance along the plane to the left, their corresponding difference in height are:
Then, the difference in potential energy of the system is:
By the definition of work:
Then:
For the acceleration along the plane, using and the total mass , the acceleration is:
For the motion over distance , starting from rest:
Thus:
The speed at time is given by:
For Exercise 2.15, the acceleration is given by:
Substituting this into the expression for speed, we get: