- #1
Better WOrld
- 80
- 1
Homework Statement
Find the minimum force ##\displaystyle F## required to move ##\displaystyle M_2##.Details and Assumptions:
##\displaystyle M_1 = 3Kg##
##\displaystyle M_2 = 5Kg##
##\displaystyle \mu_1 = 0.4##
##\displaystyle \mu_2 = 0.6##
##\displaystyle g = 9.8m/s^2##
Homework Equations
The Attempt at a Solution
[/B]
The solution suggested is as follows:
Let ##\displaystyle M_1## be displaced by a small distance ##\displaystyle x##
Using the Work energy theorem,
$$\displaystyle Fx - \mu_1M_1gx - \frac{1}{2}Kx^2 = \Delta K.E.$$
For the situation that ##\displaystyle M_2## just moves,
##\displaystyle \Delta K.E. _{M_1}= 0##
However, I cannot understand why the change in Kinetic Energy of M1 should be 0. How do we know that when M2 is just about to move, M1 will be at rest?
I've been troubled by this doubt for ages and would be really grateful if somebody would kindly explain the reason to me in detail. Many many thanks in advance!