• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Physics: Post your doubts here!


XPRS Administrator
Reaction score
a child of mass 35 kg movies down a sloping path on a skate board. the sloping path makes an angle 45 degree with the horizontal. the constant speed of the child along the path is 6.5 m/s. Calculate:
a) vertical dist through which child moves in 1.0s (done)
b) the rate at which potential energy is being lost (g=9.81 m/s^2) (confusion)

How is the answer to b) 80 J/s??

All I did was P = (35x9.81x0.51)/1 which gives answer 175 J/s (or 175 W)
vertical distance moved: sin(45)=6.5/dist
dist = 0.7071*6.5
dist = 4.596

rate at which potential energy is lost is just the energy change in one sec (i.e. vertical dist change in part A)
p.e = mgh = 35*9.81*4.596
p.e. = 1578 J/s