F1 and F2 constant forces acting
on the box as the box slides rightward across a frictionless floor. F1 is
horizontal with magnitude
2.0 N; F2 is applied upward by 60o to the floor and has magnitude 4.0 N. The speed v of the box at certain instant is 3.0 m/s.
a)What is the power due to each force acting on the box at the instant and what is the net power? Is the net power changing at
that instant
b)If the magnitude of F2 is, instead, 6.0 N, what
is the net power, and
is it changing?
P1 = F1 v cos 180 = -6.0 W
P2 = F2 v cos 60
= 6.0 W
Pnet = 0
→ K is const → v is const → Pnet is
const.
P2 = F2 v cos 60
= 9.0 W
Pnet = 3.0
W → K is inc. → v is inc. → Pnet is changing.