Two objects have masses of 17 MG17MG and 22 MG22MG. How much does the gravitational potential energy between the objects change if the distance between them changes from 55 m55m to 32 m32m?

1 Answer
Dec 29, 2017

It is increased by 72%

Explanation:

The gravitational potential energy is

U = -G(m_1*m_2)/r U=Gm1m2r

where G =6.67 xx 10^-11 (Nm)/(kg^2)=6.67×1011Nmkg2is the universal gravitational constant, m_1 and m_2m1andm2 are masses, and r is the separation between m_1 and m_2.m1andm2. Any objects that attract each other have negative potential energy; otherwise, objects that repel each other has positive potential energy.

Hence, when the distance between shrinks, the gravitation energy becomes stronger (or more negative).

Let
U_1 = -G(m_1*m_2)/r_1 = -G( 17MG*22MG)/(55m) U1=Gm1m2r1=G17MG22MG55m

U_2 = -G(m_1*m_2)/r_2 = -G( 17MG*22MG)/(32m) U2=Gm1m2r2=G17MG22MG32m

You calculate the potential energies above explicitly if you wish by substituting G with the numerical value given above, and then find their difference.

Or you can compare the final to the initial potential energy to get
:
U_2/U_1= 55/32 U2U1=5532

Then
U_2 = 55/32U_1U2=5532U1

That is, the potential has become 1.72x stronger than before.

The change is:
Delta U= U_2-U_1 = 55/32 U_1 - U_1 = 23/32U_1

The percentage change is:

(Delta U)/U_1 xx100% = 23/32 xx 100% =72%

Thus the potential energy is 72% stronger then before.