### Chapter #6 :Gravitation : Short Q/A / C.R.Q's

Q. How would the weight of the body vary as it is taken from earth to moon? What will be the effect on mass?
Ans. As we know that the weight depends on the mass of body and the acceleration due to gravity there. As the mass being the constant quantity it will not vary on the surface of moon. But the value of g on moon is one sixth the value on the surface of earth so the weight of the body will decreases 1/6 times.

Q. Gravitational force is directly proportional to the mass of the body then why all bodies fall with same velocity?
Ans. A/c to the law of gravitation
F=G m1 m2/r2
Or        mg= G Me m/ Re 2
Then    g=G Me/ Re 2
So the acceleration of any body in free fall motion is independent of mass.

Q. Suppose you are falling from a hill with a box in your hand so the weight of box during falling  experienced is grater or lesser?
Ans. As we know that in moving downward the apparent weight is less than the actual weight .i.e.
Apparent weight = (mg) – ma
In free fall motion a=g
Then                Apparent weight =mg– mg
Apparent weight =0
So the weight of the box experienced during falling is equal to zero.

Q. The Moon revolves around Earth due to gravitational force then why the apple on the earth doesn’t?
Ans. For the circular motion the force is required which attracts the body toward center of the circle and a force that pulls the body out of the circle (i.e. centripetal and centrifugal force).As the apple does not has any velocity for the centrifugal force so it is in rest whereas the earth has its velocity or the centrifugal force that’s why it moves around sun.

Q. What is the effect on the weight at the center of earth?
Ans.As we know that the weight of any body depends upon the value of g and g decreases with the depth.
g’=g (1-d/ Re 2)
at the center d=Re
then  g’=g (1- Re 2/ Re 2)
or         g’=g (1-1)
or         g’=0
Now if we are at the center of the earth the value of g becomes zero and also the weight will become zero.

### COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…