The power expended is 500 W
Explanation:
First of all, we start by calculating the work done by the man in order to ascend: this is equal to the gravitational potential energy gained by the man, which is

where
m = 50 kg is the mass of the man
is the acceleration of gravity
is the change in height
Substituting,

Now we can calculate the power expended, which is given by

where
W = 2500 J is the work done
t = 5 s is the time elapsed
Substituting, we find

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Self productive and it depends on how whom is behaving.
Answer:
0.94 m/s^2 downwards
Explanation:
m = 70 kg, m g = 70 x 9.8 = 686 N
R = 620 N
Let the acceleration be a, as the apparent weight decreases so the elevator is moving downwards with an acceleration a.
mg - R = ma
686 - 620 = 70 x a
a = 0.94 m/s^2
Answer:
Twice.
Explanation:
The momentum of an object is given by :
p = mv
Where
m is mass and v is the velocity
If the mass of the ball were doubled, m'=2m and v'=v=3 m/s
New momentum,
p'=m'v'
p'=2m × v
p'=2mv
or
p'=2p
So, the new momentum becomes twice the initial momentum.