Question Details

A planet has mass 1/10 of that of earth, while radius is 1/3 that of earth. If a person can throw a stone on earth surface to a height of 90m, then he will be able to throw the stone on that planet to a height.

Options

A

90m

B

40m

C

100m

D

45m

Correct Answer :

100m

Solution :

The correct option is 100m.

To find the height to which a person can throw a stone on the planet, we need to compare the acceleration due to gravity on the planet with that on Earth.

Step 1: Formula for acceleration due to gravity
The acceleration due to gravity (g) on the surface of a celestial body of mass M and radius R is given by the formula:
g=GMR2
where G is the universal gravitational constant.

Let the mass of Earth be Me and its radius be Re. The acceleration due to gravity on Earth is:
ge=GMeRe2

Step 2: Calculate gravity on the planet
For the planet, we are given:
Mass of the planet, Mp=110Me
Radius of the planet, Rp=13Re

Substituting these values into the formula for gravity on the planet (gp):
gp=GMpRp2=GMe10Re32

Simplifying the expression:
gp=910GMeRe2=910ge

Step 3: Relationship between height and gravity
When a stone is thrown vertically upward with an initial velocity u, the maximum height h it attains is given by the kinematic equation:
h=u22g

Assuming the person throws the stone with the same initial velocity u on both Earth and the planet, the height is inversely proportional to gravity:
h1g

Therefore, we can write the ratio of heights as:
hphe=gegp

Step 4: Calculate the height on the planet
Substitute the values of he=90 m and gp=910ge into the ratio:
hp90=ge910ge=109

Solving for hp:
hp=90×109=100 m

Thus, the person will be able to throw the stone to a height of 100m on that planet.

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