major reasoning questions for grade 10 students for SLC
chapter :1:gravitation
1)An artificial staellite doesnot need any fuel to revolve in its orbit around the earth?
ans: The gravitational force between satellite and earth provides the centripetal force required by the satellite to move in a circular orbit.Otherwise , at that height there is negligible air friction.so no fuel is required for its orbital motion.
2)Tides rise on the sea,why?
ans: Tides rise on the sea because the gravitational force on the earth due to the moon and sun.
3)An effect of gravitation is more in liquid then in solid,why?
ans: The molecules in liquid are not rigidly fixed.therefore ,the effect of gravitaion is more in liquid then in solid.
4)Why does universal gravitational constant called so?
ans:The value of G for any pair of masses in the universe is the same. on the other hand, the value of G is independent of the medium in which the masses are placed.this is why the G is called universal gravitational constant.
5)Why do newton's law of gravation called universal law?
ans : Newton's law gravitation holds true for all bodies wheather tyerrestial or celestrial. that is the force of gravitaion exists everywhere in the universe and for all bodies whether macroscopic microscopic. Therefore,i it is called universal law.
6) Why is the value of gravity less at the top of a mountain?
ans: We know that the value of gravity at a place on the surface of the earth is inversely proportional to the square of the radius or distance from the centre of the earth. The distance at the top of a mountain is greater than its foot. Therefore, the value of gravity is less at the top of a mountain than at its foot.
7) If the earth is squeezed to the size of the moon. What will be its effect on the gravity of the earth and why?
ans: If the present earth is squeezed to the size of moon, the acceleration due to gravity will be increased by about 14 times since, acceleration due to gravity is inversely proportional to the square of radius if mass is constant.
8) The acceleration due to gravity in the earth is 9.8m/s s.q,what does it mean?
ans: it means ,when a body falls freely towards the earth its velocity increases by 9.8 m/s in every second duringi its motion .
9)Why does the value of 'g' vary from place to place on the surface of the earth?
ans: on the surface of the earth , g is inversely proptional to the radius of the earth .the earth is not a perfect sphere .that is different point on the earth surface are at different distance from the centre of the earth . that is value of R vary from place to place on the surface of the earth.
10)Where is the value of 'g' greater :at the poles or at the equator,why?
ans: the value of g at a place on the earth is inversely proportional to the square of the radius of the earth at the place.the radius of the earth at a place
the radius of the earth at the poles is less than at the equator .therefore, the value of g at the poles is less then the value of g at the equator.
11)why is the value of 'g' greater in terai region than in himalayan region?
ans: we know that the value of 'g' is inversely propotional to the square of the distance of the place from the centre of the earth. the radius of the earth in himalayan region is greater than terai reagion. therefore, the value of 'g' at the poles is greater than the value of g at the equator.
12)Why is a body dropped from thesame height reaches the ground quicker at the poles than at the equator of the earth?
ans; the polar radius is less than equatorial radius of the earth. the accleration due to gravity is inversely propotional to the square of the radius .as a result,the value of g is more at poles than the equator. therefore,a body falls quicker at the poles than at the equator.
13)A man can jump six times as high on the moon than that on the earth.why?
ans: the value of g on the surface of the moon is about one-sixth of its value on the surface of the earth .as a result gravitational pull is 6 times less on the moon than the earth. therefore, a man can jump six times a high on the moon as that on the earth.
14)The probablity of getting hurt is more when a person jump from a significant height.why?
ans: Accleration due to gravity produces on the every falling body towards the earth's surface . when a body falls,there is accleration due to garvity.due to accleration .the velocity of body increases and the force also increases .in this way, the probablity of getting hurt is more when jumps from significant height.
15)An iron ball and a feather are dropped simultaneously from the same height in a vaccum . which one will strike the ground first and why?
ans: the accleration produced by the earth attraction on all bodies is same irrespective of their masses of there masses if there is no air resistence .therefore, if an iron ball and feather are dropped simultaneously in vaccum , their speed increases with the sane rate . as a result ,they reach ground together.
16)It is difficult to lift a large stone on the surface of the earth but easy to lift small one,why?
ans: the weight of a large stone is greater than a small one because large stone has greater mass then small stone.therefore,it is difficult to lift a large stone on the surface of the earth but easy to lift small one.
17)The weight of a body varies from place to place,why?
ans : the weight of a body depends upon the value of accleration due to gravity i.e W=mg. the value of 'g' varies from place to place. it is maximum at the equator and zero at the centre of the earth.therefore weight of a body varies from place to place.
18)The weight of a body is more at the polar region of the earth than at the equatorial region,why?
ans: the weight of a body at a place depends upon the valuef of 'g' at a place.the value of 'g' at a place is inversely propotional to the square of the radius of the earth.the polar radius is less than the equatorial radius .therefore ,the value of 'g' is more at pole than the equator as a result weight of a body is more at poles than the equator.
19)Why does the weight of an object decrease with increase in distance from the centre of the earth?
ans:The weight of an object depends upon the value of 'g'. the value of 'g' is inversely proportional to the square of distance of the place from the centre of the earth. that is, the value of 'g' decreases with increase in distance from the centre of the earth. as a result, weight of an object decreases with increase in distance from the centre of the earth.
20)A body is weighed at sea level and at the top of the mount everest.where will the weight be greater and why?
ans:the weight of a body at a place depends upon the value of 'g' at the place. the value of g at a place is inversely proportional to the square of the radius of the earth at the place. at sea level, the radius of the earth is less than at the top of the mount everest. It is, therefore, a body is weighed greater at sea level than at the top of the mount everest.
21)A body is taken from the equator to the pole of the earth. what happens to its weight? why?
ans:The weight of an bodyat a place depends upon the value value of 'g'at the place .the value of g at a place is inversely propotional to the square of the radius of the earth at the place.the radius of the earth is less at the poles than at the equator.it is ,therefore,when a body is taken from the equator to the pole of the earth,the weight of the body increases.
22)The weight of a body is more in terai than in mountain region.explain why?
ans: the weight of a body at a place depends upon the vqlue of "g" .the value of g at a place is inversely propotional to the square of the distance of the palce from centre of the earth .the distance that place from centre of the earth is the radius .for a place in terai,the radius is less than that in a place in the mountain region.it is therefore,the weight of a body is more in terai than in mountain region.
23)Why does the weight of a body differ on different celestrial body of the universe?
ans: the weight of a bodyina celestrial body depends on the value of g of the celestrial body.the value of g for different .it is therefore,the weight of a body differ on different celestrial bodies.
24)The weight of a body is less inside mine or cave than on the surface of the of the earth.why?
ans:as we go inside the earth the value of attracting mass decrease and hence ,the value of decrease .therefore the weight of the body mg is less inside the earth than on the surface .
25)An astronaut sitting in an artificial satellite revolving around the earth fells weightlessness,why?
ans: the accleration of the astronomer and that of the satellite revolving around the earth are equal hence ,the astronomer does not exert any force on the sides of the satellite.therefore an astronomer feels weightlessness.
26)Does a parachute fall freely?explain with reason..
ans: no a parachute does not fall freely because of the earth atmosphere.that is freefall is only possible where there is no atmosphere,but on the surface of the earth,there is atmosphere.
27)A paratropper lands safely when jumped from aeroplane,why?
ans:on jumping out from an aeroplane with parachute,the resistence due to air will be considerably high .as a result , the velocity of falling man will be low,constant and is balanced.due to this paratropper lands safetly.
28)under what condition does a feather and iron ball fall at the same rate?explain with reason .what is the accleration of the iron ball and the coin at that instant?
ans:if there is no air resistence of air or in vaccumed both a feather or iron ball at the same time .because there is no resistence of air ,all bodies irrespective of their mass fall towards the earth with the same accleration .the accleration due to gravity of both object is 9.8m/s^2.
29)Why will a sheet of a paper fall slower than one that is crumbled into a ball?
ans:the sheet of paper will experience a larger air resistence due to its larger surface area than that of its ball from.hence,the sheet falls slowly than its ball from.
30)Why did a coin and feather fall together on the surface of the moon when dropped simultaneously ?
ans:we know that on the surface of the moon ,there is no air resistence .if there is no air resistence ,the accleration produced by the moon on all bodies is the same irrespective of their masses.therefore,if a coin and a feather are dropped simultaneously on the surface at the moon,their speed increase with the same rate .as a result they reach the ground together
