STD-IX, CBSE BOARD, NCERT BOOK, GRAVITATION, MCQs ON ACCELERATION DUE TO GRAVITY (g)

1.  When a body is thrown up, the force of gravity is-

(a) in the upward direction

(b) in the downward direction

(c) zero

(d) in the horizontal direction

 

ANS: in the downward direction

 

2.  When an object is thrown up, the force of gravity-

(a) is opposite to direction of motion

(b) is in the same direction of motion

(c) becomes zero at the highest point

(d) increases as it rises up

 

ANS: is opposite to the direction of motion

 

3.  In vacuum, all freely falling objects-

(a) have the same speed

(b) have the same velocity

(c) have the same force

(d) have the same acceleration

 

ANS: have the same acceleration

 

4.  Choose the correct statement.

(a) all bodies repel each other in the universe

(b) our earth does not behave like a magnet

(c) acceleration due to gravity is 8.9 ms^-2

(d) all bodies fall at the same rate in vacuum

 

ANS: all bodies fall at the same rate in vacuum

 

5.  A heavy stone falls (if air resistance is neglected)-

(a) faster than a light stone

(b) slower than a light stone

(c) with same acceleration as a light ball falls

(d) none of these

 

ANS: with same acceleration as a light ball falls

 

6.  Two bodies A and B of mass 500 g and 200 g respectively are dropped near the earth’s surface. Let the acceleration of A and B be a_A and a_B respectively, then-

(a) a_A = a_B

(b) a_A > a_B

(c) a_A < a_B

(d) can’t say

 

ANS: a_A = a_B

 

7.  Two iron and wooden balls identical in size are released from the same height in vacuum. The time taken by them to reach the ground are-

(a) not equal

(b) exactly equal

(c) may or may not be equal

(d) zero

 

ANS: exactly equal

 

8.  A sheet of paper and another sheet of paper crumpled into a ball are dropped from the top of a tower-

(a) sheet of paper reach the ground earlier than the ball

(b) sheet of paper reach the ground later than the ball

(c) both sheet of paper and ball reach the ground simultaneously

(d) sheet of paper remains in the air

 

ANS: sheet of paper reach the ground later than the ball

 

9.  The acceleration due to gravity near the moon’s surface is-

(a) approximately equal to that near the earth’s surface

(b) approximately six time that near the earth’s surface

(c) approximately one-sixth of that near the earth’s surface

(d) slightly greater than that near the earth’s surface

 

ANS: approximately one-sixth of that near the earth’s surface

 

10.  The acceleration due to gravity is g_e on Earth and g_m on Moon-

(a) g_e = g_m

(b) g_e < g_m

(c) g_e = g_m/6

(d) g_m = g_e/6

 

ANS: g_m = g_e/6

 

11.  The value of acceleration due to gravity (g) on the surface of the earth is-

(a) 9.8 cm s^-2

(b) 9.8 km s^-2

(c) 9.8 cm s^-3

(d) 9.8 m s^-2

 

ANS: 9.8 m s^-2

 

12.  The SI unit of g is-

(a) m^-2s

(b) ms^-2

(c) sm^-2

(d) ms^-1

 

ANS: ms^-2

 

13.  The acceleration due to gravity is 9.8 ms^-2

(a) much above the earth’s surface

(b) near the earth’s surface

(c) deep inside the earth

(d) at the centre of the earth

 

ANS: near the earth’s surface

 

14.  The value of acceleration due to gravity on the surface of moon is-

(a) 9.8 cm s^-2

(b) 9.8 m s^-2

(c) 2.5 cm s^-2

(d) 1.6 m s^-2

 

ANS: 1.6 m s^-2

 

15.  The value of acceleration due to gravity is high if

(a) mass and radius both are small

(b) mass is small and radius is large

(c) mass is large and radius is small

(d) mass and radius both are large

 

ANS: mass is large and radius is small

 

16.  Suppose a planet exists whose mass and radius both are half those of Earth. Calculate the acceleration due to gravity on the surface of this planet.

(a) 19.6 m/s²

(b) 15.6 m/s²

(c) 10.6 m/s²

(d) 20 m/s²

 

ANS: 19.6 m/s²

 

17.  A particle is taken to a height R above the earth’s surface, where R is the radius of the earth. The acceleration due to gravity there is-

(a) 2.45 m/s²

(b) 4.9 m/s²

(c) 9.8 m/s²

(d) 19.6 m/s²

 

ANS: 2.45 m/s²

 

18.  When a spaceship is at a distance of two earths radius from the centre of the earth, the gravitational acceleration is-

(a) 19.6 ms^-2

(b) 9.8 ms^-2

(c) 4.9 ms^-2

(d) 2.45 ms^-2

 

ANS: 2.45 ms^-2

 

19.  If g is the acceleration due to gravity on the surface of earth, its value at a height equal to double the radius of earth is,

(a) g

(b) g/2

(c) g/3

(d) g/9

 

ANS: g/9

 

20.  What happens to the acceleration due to gravity with the increase in altitude from the surface of the earth?

(a) increases

(b) decreases

(c) first decreases and then increases

(d) remains same

 

ANS: decreases

21.  Acceleration due to gravity is maximum at (R is the radius of earth)

(a) a height R/2 from the earth’s surface

(b) the centre of the earth

(c) the surface of the earth

(d) a depth R/2 from earth’s surface

 

ANS: the surface of the earth

 

22.  If g₀, g_h and g_d be the acceleration due to gravity at earth’s surface, at height h and at a depth d respectively, then

(a) g₀ > g_h and g₀ > g_d

(b) g₀ < g_h and g₀ < g_d

(c) g₀ > g_h and g₀ < g_d

(d) g₀ < g_h and g₀ > g_d

 

ANS: g₀ > g_h and g₀ > g_d

 

23.  The value of ‘g’ is zero-

(a) at the top of the atmosphere

(b) at 20 km below the surface of the earth

(c) at 20 km above the surface of the earth

(d) at the centre of the earth

 

ANS: at the centre of the earth

 

24.  The acceleration due to gravity-

(a) has the same value everywhere is space

(b) has the same value everywhere on the earth

(c) varies with the latitude on the earth

(d) is greater on moon because it has smaller diameter

 

ANS: varies with the latitude on the earth

 

25.  The value of ‘g’ at pole is-

(a) greater than the value at the equator

(b) less than the value at the equator

(c) equal to the value at the equator

(d) none of these

 

ANS: greater than the value at the equator

 

26.  The value of ‘g’-

(a) is least on equator

(b) is least on poles

(c) is same on equator and poles

(d) increases from pole to equator

 

ANS: is least on equator

 

27.  The value of ‘g’ will be maximum at-

(a) the equator

(b) the top of Mount Everest

(c) the poles of the earth

(d) the Kutab Minar

 

ANS: the poles of the earth

 

28.  A particle is dropped from a tower 180 m high. How long does it take to reach the ground?

(a) 2 s

(b) 6 s

(c) 5 s

(d) 8 s

 

ANS: 6 s

 

29.  A stone dropped from a building top takes 4 s to reach the ground. The height of the building is-

(a) 78.4 m

(b) 19.6 m

(c) 156.8 m

(d) 78.9 m

 

ANS: 78.4 m

 

From the second equation of motion, h = ut + ½ gt²

Put u=0 and g=9.8 m/s²

 

30.  A student drops a ball from the top of tower of height 19.6 m. The velocity with which the ball hits the ground is-

(a) 9.8 m/s

(b) 19.6 m/s

(c) 12.8 m/s

(d) 39.2 m/s

 

ANS: 19.6 m/s

 

31.  A ball is thrown up and attains a maximum height of 19.6 m. Its initial speed was-

(a) 9.8 ms^-1

(b) 44.3 ms^-1

(c) 19.6 ms^-1

(d) 98 ms^-1

 

ANS: 19.6 ms^-1

 

32.  A stone dropped from the bridge hits water after 2 seconds. If acceleration of the stone is 9.8 m/s², then height of the bridge is-

(a) 4.9 m

(b) 9.8 m

(c) 19.6 m

(d) 39.2 m

 

ANS: 19.6 m

 

33.  A body is thrown up with a velocity of 20 ms^-1_. The maximum height attained by it is approximately-

(a) 80 m

(b) 60 m

(c) 40 m

(d) 20 m

 

ANS: 20 m

 

34.  A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when the two stones will meet.

(a) 4 s

(b) 3.6 s

(c) 2 s

(d) 8 s

 

ANS: 4 s

 

35.  A stone drops from the edge of the roof. It passes a window 2 m high in 0.1 s. How far is the roof above the top of the window?

(a) 15 m

(b) 1.5 m

(c) 10 m

(d) 19.4 m

 

ANS: 19.4 m

 

36.  A boy on a cliff 49 m high drops a stone. One second later, he throws a second stone after the first. They both hit the ground at the same time. With what speed did he throw the second stone?

(a) 12.1 m/s

(b) 0.60 m/s

(c) 54 m/s

(d) 60 m/s