Question

Question
1.
An object of mass 'm' is dropped from a height
"h' above the surface of earth. What will be its
velocity just before reaching the surface of
earth?​

Answer 1

Answer:

v=gR

Explanation:

Suppose a particle of mass m is at a distance R from earth's surface. At this point its K.E is 0 and P.E is (

2R

−GMm

), where M is the mass of earth.

On the surface of earth, the P.E of the particle will be (

R

−GMm

) and it P.E will be say (

2

1

)mv

2

.

Now the total energy in these two cases will be same.

−

2R

GMm

+0=−

R

GMm

+

2

1

mv

2

2R

GMm

=

2

1

mv

2

v=

R

GM

but g=

R

2

GM

gR=

R

GM

So, v=

gR