Some one pls help answer urgently!

The radius of the planet Venus is nearly thesame as that of the earth but it's mass is only 80% that of the earth. If an object weighs 0.8 on the earth what does it weigh on Venus?
Calculate the value of g on venus.

Thanks

I hope you can understand it

Concluding solution

blendz4real:
Some one pls help answer urgently!

The radius of the planet Venus is nearly thesame as that of the earth but it's mass is only 80% that of the earth. If an object weighs 0.8 on the earth what does it weigh on Venus?
Calculate the value of g on venus.

Thanks

Since the radius of Venus, R_v , and the radius of Earth, R_e , are nearly the same(ie. approximately equal) and no further information is given on their relative sizes, we assume that

R_v = R_e = R

By Newton's law of gravitation, we have the following

On a planet of mass, M , and radius, r , the weight, W, of an object of mass, m , is given by
W = (GMm)/r² = mg
Where:
g = the acceleration due to gravity on the planet, and
G = the gravitational constant

From the question, the mass of Venus, M_v , and the mass of Earth, M_e are given by

M_v = (4/5)M_e

The weights of the object on Venus and Earth,W_v & W_e = 0.8 respectively, are given by

W_v = (GM_vm)/R² = [(4/5)(GM_em)]/R² = mg_v ———(1)
W_e = (GM_em)/R² = mg_e ———(2)

g_e = 9.8 m/s²
g_v =?

Equations (1) & (2) can be rewritten as follows

(5/4)W_v = W_e = (GM_em)/R²

——and——

m = W_v/g_v = W_e/g_e

(5/4)W_v = 0.8
W_v = (4/5) × 0.8 = 0.64

0.8/9.8 = 0.64/g_v
g_v = (0.64 × 9.8 )/0.8 = 7.84 m/s²

..

gensteejay:
Concluding solution

Thanks for your input.

Martinez39:
Since the radius of Venus, R_v , and the radius of Earth, R_e , are nearly the same(ie. approximately equal) and no further information is given on their relative sizes, we assume that


By Newton's law of gravitation, we have the following


From the question, the mass of Venus, M_v , and the mass of Earth, M_e are given by


The weights of the object on Venus and Earth,W_v & W_e = 0.8 respectively, are given by


Equations (1) & (2) can be rewritten as follows


(5/4)W_v = 0.8[/i] [/font]
W_v = (4/5) × 0.8 = 0.64

0.8/9.8 = 0.64/g_v
g_v = (0.64 × 9.8 )/0.8 = 7.84 m/s²

Thanks alot.... I appreciate