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Q.24. We do not get hurt, we jump with parachute. Why?

Parachute pens and expands when parachutists jump towards the earth

due to air resistance created by the earth’s atmosphere. Larger the area of

the parachute, more will be the upthrust generated by the resistance of air.

As a result, the acceleration of parachute decreases since velocity goes on

decreasing and finally the velocity turn up in uniform velocity. Due to which

the parachutists can balance their body and do not get hurt, when jump

with parachute.

Q.25. Astronaut feels weightlessness in a space craft. Why?

During the orbit of the spacecraft on the earth, the direction of circular

motion of spacecraft gets changed at every point(i.e.. it gets accelerated).

So, direction of acceleration is towards the centre of rotation. The

centripetal force helps the spacecraft to be more in circular path which is

provided by gravitational force of the earth. So, astronaut and spacecraft

are in continuous state of free fall. There is no force between spacecraft and

astronaut ( i.e.. the acceleration of the astronaut with respect to the satellite

is zero). So, the astronaut feels weightlessness in a spacecraft.