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AikiGirl
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Homework Statement
A uniform solid sphere rolls on a horizontal surface at 20m.s^-1 and then rolls up an incline which has an angle on inclination of 30°. Ignoring friction, calculate the height attained by the sphere.
Homework Equations
Weren't given any specific equations to work with but here are some I've attempted to use:
Ek(lin)= 1/2 mv^2, Ek(rot)=1/2 Iw^2, Ep=mgh, Vf=Vi+at, D=Vi t + 1/2 at^2
The Attempt at a Solution
As it is a uniform sphere I ignored Ek(rot). We were given an answer of 29m.
E(before)=E(after)
Ek+Ep=Ek+Ep
1/2mv^2 +mgh= 1/2mv^2 +mgh (masses cancel)
0.5x20^2 + 9.8x0 = 0.5 (20/cos30)^2 + 9.8h Not sure if this is the right one to use
200 = 266.67 + 9.8h
-66.67 = 9.8h
h= - 6.8
So I tried looking at just the vertical component:
Vf=Vi+at
0=(20tan30) + 9.8 t
9.8t=11.55
t=1.18s
D=Vi t + 1/2 at^2
D=11.55 x 1.18 + 0.5 x 9.8 x 1.18^2
D= 20.41m
Does anyone see where I went wrong? Any help would be greatly appreciated!