SCIENCE

                                         physics                                      

                                                        FORCE                    

1. Is the falling of  “Para­chute” on the earth’s sur­face free fall?

Ans: No, the falling of Para­chute on the earth’s sur­face is not free fall because it has larger sur­face area due to which it offers the larger air resis­tance which decreases the accel­er­a­tion of the para­chute so, the para­chute will fall towards the earth’s sur­face approx­i­mately with con­stant velocity.

2. Why does a per­son in space­craft feels weightlessness?

Ans: Dur­ing the orbit of 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 move in a cir­cu­lar path which is pro­vided by grav­i­ta­tional force of earth. So, the astro­naut and space­craft are in con­tin­u­ous state of free fall. There exists no force between space­craft and astro­naut. This gives the impres­sion of freefall and the per­son inside space­craft feels weightlessness.

3. At what con­di­tion does the body hav­ing fixed mass have zero weight?

i. When the body falls freely under the action of gravity.

ii. When the body is in outer space away from the earth’s grav­i­ta­tional field where the force of grav­ity is zero

4.  Weight of body is more in polar region than in equa­to­r­ial region of the earth. Why?

Ans: As we know  . The value of grav­ity ‘g’ is more at poles than at equa­tor i.e   as radius is less at poles com­pared to equa­tor.  Hence, weight of a body is greater at pole than  at the equator.

5. In real life, objects have no com­plete freefall?

Ans: In real life, objects have no com­plete freefall because there is always the pres­ence of air resis­tance in this world.

6. Weight of body is less on the moon than on the earth. Why?

Weight of body is directly pro­por­tional to g (i.e.   ) . The ‘g’ of earth is 6 times greater than that of moon. Thus the weight of body is less on the moon than on the earth.

7. G is called uni­ver­sal grav­i­ta­tional con­stant, Why?

Ans: G is called uni­ver­sal grav­i­ta­tional con­stant because the vale of G remains con­stant every­where ie.   and it is not affected by any medium i.e. air, water etc.

8. Newton’s law of grav­i­ta­tion is called uni­ver­sal law. Why

Newton’s law of grav­i­ta­tion is called uni­ver­sal law because it is applied for any object that may be very small (micro ) objects as well as very large (macro) objects.

9. It safe when jumped from aero­plane with the help of parachute?

The para­chute has more air resis­tance due to its large shape and size. After falling cer­tain dis­tance, the upward force of air resis­tance equals to the down­ward force of grav­ity and a man with para­chute falls with uni­form veloc­ity. Thus, it is safe when jumped from aero­plane with the help of parachute.

10. Among moon, earth and Jupiter, which one will have more grav­ity and why?

Ans: Among moon, the earth and Jupiter, JUPITER will have more grav­ity because grav­ity of planet depends upon mass (i.e.   ). Since the Jupiter has more mass than earth and moon its grav­ity is more.

11. What is grav­i­ta­tional field intensity?

Ans: The grav­ity that applies to an object of unit mass present on the sur­face of the planet or satel­lite, is known as grav­i­ta­tional field inten­sity of a planet.

12. An iron ball and feather are dropped simul­ta­ne­ously from the same height in vac­cum which one will strike the ground first and why?

An iron ball as well as feather both will strike the ground at the same time with the same accel­er­a­tion because in the absence of air resis­tance in vac­uum both the bod­ies falls freely on the ground. Thus both bod­ies irre­spec­tive to their masses fall at the same time.

13. If a body is dropped from same height in an equa­tor and pole from which place the body will reach the ground faster?

The body will reach the ground faster from the poles because the value of g at poles is greater than the value of g at equa­tor. So, more the value of g, less will be the time taken by a body to fall from the pole.

14. One can jump higher on the sur­face of the moon than on the earth sur­face, why?

Since we know that accel­er­a­tion due to grav­ity of planet depends upon the mass of the planet. In com­par­i­son to earth, moon has less grav­ity because mass of moon is less than the mass of the earth. So, one can jump higher on the sur­face of the moon than on the earth sur­face.

15. The accel­er­a­tion due to grav­ity in the earth is   . What does it mean?

Ans: The accel­er­a­tion due to grav­ity in the earth is    it means the veloc­ity of the body increases at the rate of 9.8m/s.

16. It is dif­fi­cult to lift a large stone on the sur­face of the earth but easy to lift small one. Why?

Ans: It is so because large stone has more force of attrac­tion of the earth as it has more mass (i.e. F = mg) But, the smaller one has less force of attrac­tion as it has less mass. So, it is eas­ier to lift small stone than large stone.

 17. Why the weight of a body decrease with increase in dis­tance from the cen­tre of the earth?

Ans: The weight of a body decrease with increase in dis­tance from the cen­tre of the earth because weight is inversely pro­por­tional to the square of the dis­tance i.e.   . Hence, weight depends upon dis­tance between two bod­ies. i.e. earth and the object)

18. What is the con­clu­sion of feather and coin experiment?

Ans: Accel­er­a­tion due to grav­ity doesn’t depend upon the mass of the body. More the sur­face area of the body, more will be the air resis­tance which decreases accel­er­a­tion due to gravity.

19. There is no use of para­chute on the moon. Why?

Ans: The para­chute falls freely with accel­er­a­tion due to grav­ity on the moon due to absence of air resis­tance as there is no atmos­phere. Hence there is no use of para­chute on the moon.

20. Weight of the body at the cen­tre of the earth is zero. Why

Ans: Since the value of accel­er­a­tion due to grav­ity is zero at the cen­tre of the earth, the weight of a body is zero at the cen­tre of the earth.