To me, this question seems to lend itself to a conservation of energy approach.

At the base of the bridge, your total energy is just your initial K.E.

At the top of the bridge, your total energy is your final K.E. plus the P.E. you gain by rising height 5.2 m from the ground.

If you calculate these based on the values you give, using

KEi = KEf + PE
1/2 mvi^2 = 1/2 mvf^2 +mgh

you can easily see that they are not equal. The difference between them is the amount of work it took you to get to the top of the bridge.

I.e., the real "conservation of energy" equation (quotes added because it's not technically conservation anymore if you're adding energy to the system by means of work) should be

KEi + W = KEf + PE

For part b), isn't this just going to be the work from part a)? You're the only one doing work here--pedaling yourself to the top of the bridge.

Hope that helps!
Source(s):
my brain


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