Answer:
a) Instantaneous rate at which the force does work on the object = -6 W
b) 
Explanation:
a) Given that

and

Instantaneous rate at which the force does work on the object is called power.
Power is the dot product of force and velocity.

Instantaneous rate at which the force does work on the object = -6 W
b) Here given that 
Power = -12 W


Answer:
Hydrogen fuel cells have a higher energy efficiency. Hydrogen fuel cells create less pollution. Burning fossil fuels relies on outdated devices and technology. Pure hydrogen is more readily available than fossil fuels
Explanation:
Answer:
The hydrogen peroxide decomposes as: 
Explanation:
Hydrogen peroxide antiseptic although tightly capped but left on the shelf for a long time leads to swollen bottle and opens with a hissing sound because hydrogen peroxide reacts with air in presence of light to dissociate into water and oxygen molecules that leads to high volume of content in the tightly closed bottle and formation of water molecules from hydrogen peroxide.
Once the hydrogen peroxide has turned into water molecules it is no longer effective as an antiseptic.
When light moves from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle above which there is no refracted ray, and it is given by:

(2)
where

is the refractive index of the second medium and

is the refractive index of the first medium.
We can find the ratio

by using Snell's law:

(1)
where

is the angle of incidence

is the angle of refraction
By using the data of the problem and re-arranging (1), we find

and if we use eq.(2) we can now find the value of the critical angle:
Answer:
the free-fall acceleration on the moon is 1.68 m/s^2
Explanation:
recall the formula for the gravitational potential energy (under acceleration of gravity "g"):
PE = m * g * h
replacing with our values for the problem:
46 J = 91 * g * 0.3
solve for the "g" on the Moon:
g = 46 / (91 * 0.3)
g = 1.68 m/s^2