required to hold an object from the restraining force which gives the impression of welg WEIGHTLESSNESS IN AN ELEVATOR An elevator is a non-inertial frame of reference moving up or down with some

acceleration. tne ceiling of an elevator. The reading of the spring balance will give the tension that is acting upward on the block. Consider a block of mass 'm' suspended from a spring balance that is attached to CASE I: WHEN ELEVA TOR IS AT REST Suppose the elevaror is stationary (a = 0). Consider the forces acting on the suspended block. (1) Weight (W), acting vertically downward. (il) Tension (T). acting upward along the spring The tension is equal but opposite to thc force of gravity (W). This represents the "truc weight" of the bleck

Since net force in zero, hence T-mg Conclusion:

The : For planct. BR

(100e) 100 (2) &=3 GMe Putting cq 1 la (2) ve bave E3g 3 x 9.6 2,= 29.4ms A satellite orbits the earth 160km above the surface with speed 780E Calculate the period and speed of the satellite. (Given re = 6370 km, Me = 6.0 x 10 kg).

AP.6.7

Solution Data:

160 km, r= re +h = 6370+ 160) = 6530 km = 6.53 >x 10°m Calculations:Centripetai force griv. force mv GMem GMe 6.67x 10x6.0* 10 6.123 x 10 = 7.828 x 10 6.53 x 13

V 7828 m/s

i)vt = distancev= 27r T2Tt2x 3.14 x 6.53 x 10 1.008 7828 7828x 10 T5238.6s-238.6

h 60 x 6U T=145 hahen So the estraining force is zero

Conclusion: The apparent weight of the body is zero, although the fonce of graity s ser appon the body. 1his is called "weigthlessness

WEIGHTLESSNESS IN SATELLITE:  Discuss weightiessness in a satellite. Ans: Weight a body in s frame of reference is equal but opposite to the force tha prevents it from falling in that relerence