science
posted by anoynomous .
a weightlifter raises a 200kg barbell with an acceleration of 3 m/s. How much force does the weightlifter use to raise the barb?

To maintain the weight at the same place, the force required is mg.
To accelerate upwards at acceleration a=3m/s², he/she must apply an additional force of ma.
So the total force is
m(g+a) N
where
m=mass of weight
g=acceleration due to gravity
a=acceleration upwards. 
400kg

A weightlifter raises a 200kg barbell through a height of 2 m in 2.2 s. The average power he develops during the lift is