How Much Electrical Power Does a 75% Efficient Pedal-Operated Generator Produce?

[lemon]

Hi:
Would somebody please check to see if I am on the right track with this problem.
Many thanks

Homework Statement

An 80kg man on a step-exercise machine climbs a staircase 3.0m high in 8.5s. If he works at the same rate to drive a pedal-operated generator with an efficiency of 75%, how much electrical power would be produced?

Homework Equations

power=work done/time taken
efficiency=useful energy output/total energy input
work=force x displacement in direction of force
F=ma
weight=mg (gravity=10ms ^-2)

The Attempt at a Solution

F=80 x 10 =800N
Work done (W)=800 x 3.0 = 2400J
Power=2400/8.5 = 282.4W (1d.p.)
therefore
75% x 282.4 = 211.8W
F=

 

[xcvxcvvc]

looks good

 

[lemon]

thank you