Answer:
180 W
Explanation:
The work done by the man against gravity is equal to its gain in gravitational potential energy:

where
(mg) = 720 N is the weight of the man
is the change in height
Substituting,

The power he must deliver is given by

where
W = 3600 J
t = 20 s is the time taken
Substituting,

Answer:
103.1 V
Explanation:
We are given that
Initial circumference=C=168 cm

Magnetic field,B=0.9 T
We have to find the magnitude of the emf induced in the loop after exactly time 8 s has passed since the circumference of the loop started to decrease.
Magnetic flux=
Circumference,C=

cm



When t=0



E=

t=8 s
B=0.9


The volume of the object must be no larger than
.
Explanation:
In order for an object to be able to float in water, its density must be equal or smaller than the water density.
The density of water is:

This means that the density of the object must be no larger than this value.
We also know that the density of an object is given by

where
m is the mass of the object
V is its volume
For the object in this problem, the mass is

Therefore, we can re-arrange the equation to find its volume:

So, the volume of the object must be no larger than
.
Learn more about density:
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Answer:
Explanation:
Given
mass of spring 
extension in spring 
downward velocity 
Position in undamped free vibration is given by

where 
also 



it is given


substituting values we get






