Find speed?

You are on roller blades on top of a hill. Your potential energy is equal to 1000 joules. The last time you checked, your mass was 60 kg.





a. What is your your weight in newtons? ( I got 588N )


b. What is the height of the hill? ( I got 16.7 meters )


c. If you start skating down this hill, your potential energy will be converted to kinetic energy. AT the bottom of the hill, your kinetic energy will be equal to your potential energy at the top. What will be your speed at the bottom of the hill?

Find speed?
a) you are correct with g=9.8


b) 588*h=1000


1.7 meters





c) 1000=.5*60*v^2


5.77 m/s


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Reply:a) w = mg


w = 60kg x 9.80 m/s^2


w = 588 N ANS





b) P.E.g = mgh


1000 J = 588h


h = 1000 J/588 N


h = 1.7 m (Are you sure the P.E. = 1000 joules?)





c) P.E.g = K.E.f


1000 J = (1/2)(588/9.8)(Vf)^2


Vf = sqrt[1000J/(1/2)(588/9.8)]


Vf = 5.8 m/s ANS





teddy boy
Reply:a. 588 N is correct


b. PE = m*g*h therefore h = (PE) / mg = 1.7 meters


c. We know that PE = KE





Since PE = mgh and KE = 1/2 mv^2


we have


mgh = 1/2 mv^2





cancel the 'm's


gh = 1/2 v^2





solve for v


v = sqrt (2gh) = sqrt (2*9.81*1.7) = 5.77 m/s
Reply:Energy and work are basically the same thing.





a) Weight is force of gravity on you. So:


Fg = mg


= 60 * 9.8


= Some number





b) Height of the hill. Eg = mgh


Eg is gravitational potential energy, m is mass, g is 9.8, and h is height.





h = Eg/mg


h = 1000/(60 * 9.8)


h = Some number





c) Ek = Eg


Ek = 1/2mv^2


v = sqrt(2Ek/m)





Ek is kinetic energy. Since all of your potential E is converted to kinetic, equate Ek = Eg and solve for v.



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