Please look at the attached awesome drawing.
Both answers are there.
Answer:
(a) work required to lift the object is 1029 J
(b) the gravitational potential energy gained by this object is 1029 J
Explanation:
Given;
mass of the object, m = 35 kg
height through which the object was lifted, h = 3 m
(a) work required to lift the object
W = F x d
W = (mg) x h
W = 35 x 9.8 x 3
W = 1029 J
(b) the gravitational potential energy gained by this object is calculated as;
ΔP.E = Pf - Pi
where;
Pi is the initial gravitational potential energy, at initial height (hi = 0)
ΔP.E = (35 x 9.8 x 3) - (35 x 9.8 x 0)
ΔP.E = 1029 J
We know: θ = ωo t + 1/2*α*t^2
so, α = 2*(θ - ωo t ) / t^2
Given: angular velocity = 96.0 rad/sectime = 7 secangular distance travelled = 28 rev
We know, In one revolution it completes 360 degrees = 6.28319 radangular distance traveled = 28 rev * 6.28319 rad
So, angular acceleration = 2*(28*6.28 - 96*7) / 7^2 = -20.25 rad/sec^2