Hi, i have a WEP related question regarding mixing work
and energy
So here it is (i came up with it and i dont quite understand the
work done by applied force)
A box is on an inclined plane and it is pushed down. at its
final position Y, it has a speed of 1m/s. the distance covered on
the plane is 5m, the total resistive force is 200N and the mass of
the box is 20kg. the distance vertically upwards to the original
box position X, is 3m
1) find the KE at X.(this one is self explainatory)
KE=1/2 x 20 x 1^2= 10J
2) What is the work done by gravity
WD by gravity= mgh=20 x 10 x 3 = 600J
3) what is the work done against resistive forces?
WD against resistive forces=200 x 5=1000J
4) what is the applied force?
(this part i dont understand, usually WD by applied force is
Applied Force X Distance Covered. But in this case we dont have the
applied force. in another example that i did once, the box was
moving upwards so the equation is
WD by applied force= WD against resistive +KE+WD against
gravity
But now im not very sure if i should plus the work done by
gravity. This is what im thinking
WD by applied force= WD against resistive + KE [im thinking
this as WD by gravity is done BY gravity so it should not include
in this? however im also thinking like this
WD by applied force= WD against resistive+KE +WD by gravity [im
thinking like this as at 3m high it has a GPE of 600J
But in the second case if wat im thinking is true it gets even
more complicated for me as i thought WD by gravity is a loss in
GPE, so pls ecplain these parts to me. Thanks so much for the
help