Recent content by yihloong

oh, then i must be misunderstanding the question

i don't think you can substitutes t2 = k2r3, because that's what they want to show, so you should have a series of steps which finally leads to t= a2/3. another hint: derivation of Kepler's third law start with F=mv2/r , or any equivalent formula for centripetal force, due to it's a circular...

i think it is safe to assume the mean distance of an elliptical orbit = [ (semi major + semi minor )/2 ] , is approximately equal to the radius of a circular orbit. hence, F=mv2/r or mv2/a is applicable.

since it's a ramp, the normal force would not equal to the weight of object.

in my point of view, the question start by asking you to show, therefore you should start with the derivation/proof for Kepler's third law. hint: Kepler third law is about the orbits of planets, so think of any equations that applicable to the orbit of a planet.

may i know how do you get this?

you have used the correct equations, but you forget about the focal length of convex mirror is virtual, hence you should substitutes f = -25 cm, and you should get di = -20 cm , hence, hi = 0.80 cm