When an object is thrown up, the force of gravity

1

(a)

acts in the direction of motion

(b)

acts in the direction opposite to the motion

(c)

remains constant as the body moves up

(d)

increases as the body moves up

The earth attracts a body with a force of 10 N. with what force does that the body attracts the earth?

1

(a)

10 N

(b)

1 N

(c)

2 N

(d)

\(\frac{1}{10}\) N

If the distance force of masses is doubled, the force between them will be

1

(a)

\(\frac{1}{4}\)times

(b)

4 times

(c)

\(\frac{1}{2}\)times

(d)

2 times

The value of acceleration due to gravity near the earth's surface is

1

(a)

8.9 m^-2

(b)

9.8 ms^-2

(c)

8.9 cms^-2

(d)

9.8 cms^-2

All bodies whether large or small fall with the

1

(a)

same force

(b)

same acceleration

(c)

same velocity

(d)

same momentum

The mass and diameter of a planet have twice the values of the corresponding parameters of the earth. Acceleration due to gravity on the surface of the planet is 

1

(a)

9.8 m/s²

(b)

4.9m/s²

(c)

980 m/s²

(d)

19.6 m/s²

When an object falls freely to the earth, the force of the gravity is

1

(a)

opposite to the direction of motion

(b)

in the same direction as that of motion

(c)

zero

(d)

constant

The force of gravitation between two bodies does not depend on

1

(a)

their separation

(b)

the product of their masses

(c)

the sum of their masses

(d)

the gravitational constant

The weight of a body of mass 1 kg on earth is

1

(a)

1 kg

(b)

1 N

(c)

9.8 N

(d)

none of these

10 kg wt is equal to

1

(a)

9.8 N

(b)

98 N

(c)

980 N

(d)

\(\frac{1}{9.8}\)N

When a spaceship is two Earth radii distant from the centre of the earth, it's gravitational acceleration is

1

(a)

19.6 m/s²

(b)

9.8 m/s²

(c)

4.9 m/s²

(d)

2.45 m/s²

The acceleration due to gravity

1

(a)

has the same value everywhere in space 

(b)

has the same value everywhere on earth

(c)

varies with the latitude on the earth

(d)

is greater on the moon due to its smaller diameter

A stone is dropped from a cliff. Its speed after it has fallen 100 m is

1

(a)

9.8 m/s

(b)

44.2 m

(c)

156.8 m

(d)

78.4 m

When an object is thrown up, the force of gravity is

1

(a)

opposite to the direction of motion

(b)

in the same direction as the direction of motion

(c)

constant

(d)

increases as it rises up

The force of gravitation between two bodies varies with r as

1

(a)

\(r^2\)

(b)

r

(c)

1/r

(d)

1/\(r^2\)

Distinguish between the terms gravitation and gravity, giving suitable examples.

2

(a)

List three phenomena which can be explained by applying universal law of gravitation.

2

(a)

State the source of centripetal force that a planet requires to revolve around the sun. On what factors does this force depend? Suppose this force suddenly becomes Zero, then in which direction will the begin to move if no other celestial body affects it? Justify your answer.

3

(a)

The mass of planet Jupiter is 1.9 x 10²⁷ kg and that of the sun is 1.99 x 10³⁰ kg. The mean distance of the Jupiter from the sun is 7.8 x 10¹¹ m. Calculate the gravitational force which the sun exerts on Jupiter.

3

(a)

Calculate the acceleration due to gravity on the moon's surface using the following data:
Mass of the earth = 6 x 10²⁴kg,
Mass of the Moon = 7.3 x 10²²kg
Radius of the earth = =6400 km,
Radius of the Moon = 1740 km.
'g' on earth's surface = 9.82 m/s².

3

(a)

How much pressure will a man of weight 80 kg f exert on the ground if 
(i) he is lying and
(ii) he is standing on his feet? Given that the area of the body of the man is 0.6 m² and that of a foot is 80 cm².

3

(a)

What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?

3

(a)

Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10²⁴ kg and of the Sun = 2 × 10³⁰ kg. The average distance between the two is 1.5 × 10¹¹ m.

5

(a)

A ball thrown up vertically returns to the thrower after 6 s. Find
(a) the velocity with which it was thrown up,
(b) the maximum height it reaches, and
(c) its position after 4 s.

5

(a)