Originally posted by gunner77:
but the answer sheet write " as the pendulum comes to rest, the potential energy and kinetic energy is converted to heat energy in overcoming air resistance. "how come got heat energy?
let's say is pendulum stops moving after swinging around.
pendulum experience air resistance. air resistance is like friction. friction means heat lost.
Originally posted by skythewood:A) work done = force x distance
work done per second = force x distanced moved per secondB) power = work done per second. same as A
C) i) horizontal force (200) = work done + friction
ii) since the box is not accelerating, net force = ma, net force = 0. so refer to above equation.
i understand the part A already
but for B and C
i thought the formula for power is work done / time
so its 50/0.25 =200?
power = 200?
part C : since the horizontal force is 200n
then the work done is 50 so fiction suppose to be 200-50 = 150 ?
Originally posted by gunner77:
i understand the part A alreadybut for B and C
i thought the formula for power is work done / time
so its 50/0.25 =200?
power = 200?
part C : since the horizontal force is 200n
then the work done is 50 so fiction suppose to be 200-50 = 150 ?
time is not 0.25 what.
0.25 means 0.25 metres moved in one sec. So when they asked per sec it means 0.25* 200
if you wanna know why and you cannot rationalise it. This is how:(write it down cos thsi is complicating when you write it out in words)
distance/speed = time
work done = distance * force
power = work done / time
power = distance * force / (distance/speed)
= force * speed
Just know that constant speed means 0 net force due to the formula. and 0 net force must mean friction is = force applied.
ohh ok i understand
no resultant force so the 200n is frictional force
thanks everyone!
what he said.