Question

38.A satellite moves around the earth in a circular orbit with speed 'V'.If 'm' is mass of the satellite then its total energy is ----------------
39.If R is radius of the earth and W is work done in lifting a body from the ground to an altitude R,the work which should be done in lifting it further to twice that altitude is -------------
40ThePEof three objects of masses 1kg ,2kg, and 3kg placed at the three vertices of an equileteral triangle of side 20cm is -------------

Answer 1

38. mass= 'm'

Velocity= 'v'

K.E= 1/2mv^2

39.Work done = increase in gravitational potential energy

W1=mgR1+RR=mgR2

[Δu=mgh1+hR] Where 'h' height above the earth surface

Given 2W2=W1

Where W2 = work done in lifting

through a height 'h'

mgR2=2mgh1+hR

Solving we get,

h=R3

40.U=−Gm1m2r−Gm2m3r−Gm1m3r

Here, r ( 0.2 m) is lebgth of the side of the triangle.

Calculation of potential energy:

U=−(6.67×10−11)(1)(2)0.2−(6.67×10−11)(2)(3)0.2−(6.67×10−11)(1)(3)0.2 =−11(6.67×10−11)0.2 =−3.7×10−9 J