Gravitation Worksheet-7

Gravitation Worksheet-7

 

  1. A man weighs 600 N on the earth. What is his mass ? (take g = 10 m/s2). If he were taken to the moon, his weight would be 100 N. What is his mass on the moon ? What is the acceleration due to gravity on the moon ? 

 

  1. How much would a 70 kg man weigh on the moon ? What would be his mass on the earth and on the moon ? (Acceleration due gravity on moon = 1.63 m/s2)

 

  1. An object of mass 50 g has a volume of 20 cm3. Calculate the density of the object. If the density of water be 1 g/ cm3, state whether the object will float or sink in water.

 

  1. The relative density of silver is 10.8 If the density of water be 1.0 × 103 kg m–3, calculate the density of silver in SI units.

 

  1. The volume of a solid of mass 500 g is 350 cm3

(a) What will be the density of this solid?

(b) What will be the mass of water displaced by this solid?

(c) What will be the relative density of the solid?

(d) Will it float or sink in water?

 

  1. What is the value of gravitational constant G (i) on the earth, and (ii) on the moon?

 

  1. Which force is responsible for the moon revolving round the earth?

 

  1. Does the acceleration produced in a freely falling body depend on the mass of the body?

 

  1. Name the scientist who gave the three laws of planetary motion.

 

  1. Name the scientist who explained the motion of planets on the basis of gravitational force between the sun and planets.

 

Answer:

  1. First of all let’s find out the mass of man on the earth  by using the formula:

          W = m × g

Here, weight of man on earth, W = 600 N

          Mass of man on earth, m = ?          

And, Acceleration due to gravity, g = 10 m s–2

Now, putting these values in the above formula, we get :

          600 = m × 10

          m = 60 kg

Hence the mass of man on the earth is 60 kilograms. Since the mass of a body remains the same everywhere in the universe. So, the mass of this man on the moon will also be 60 kilograms.

Let’s calculate the value of acceleration due to gravity on the moon by using the same formula :

          W = m × g

Now, weight of man on the moon, W = 100 N

Mass of the man on moon, m = 60 kg (Calculated)

And, Acceleration due to gravity, g = ?                       

          (on the moon)

By putting these values in the formula, we get :

          100 = 60 × g

So, g = 1.66 m s–2

thus, the acceleration due gravity on the surface of the moon is 1.66 m s–2.

 

  1. Let’s calculate the weight of the man on the moon.

Here, Mass of the man on moon, m = 70 kg

Acceleration due to gravity, g = 1.63 m/s2

                   (on the moon)

We know that : W = m × g

So, W = 70 × 1.63

          W = 114.1 N

Hence weight of the man will be 114.1 newtons on the moon. Since mass of a body is constant everywhere in the universe. The mass will be 70 kg on the earth as well as on the moon.     

 

Here,      Mass of the object = 50 g

And,   Volume of the object = 20 cm3

Density of object = 2.5 g/cm3

Thus, the density of object is 2.5 g/cm3. Since the density of the object is greater than the density of water so the object will sink in the water.

 

  1. We know that :

Relative density of substance

Here,    Relative density of silver = 10.8

                            Density of silver = ?              

Density of water = 1.0 × 103 kg m–3

So, Density of silver = 10.8 × 1.0 × 103 kg m–3

                                    = 10.8 × 103 kg m–3

Thus, the density of silver in SI units is 10.8 × 103 kg m–3

 

  1. Density of solid =

          = 1.42 g/cm3.

(b) The solid will displace water equal to its own volume.  Now, volume of water displaced is 350 cm3 and the density of water in is1 g/cm3.

Density of water

We get, 1 g/cm3

So, Mass of water = 1 g/cm3 × 350 cm3 = 350 g

Thus, the mass of water displaced is 350 grams.

(c) Relative density of solid

          = 1.42

Thus, the relative density of the solid is 1.42.

(d) Since the relative density of this solid is greater than the relative density of water  therefore, this solid is heavier than water so it will sink in water.

 

  1. 6.67 × 10–11 Nm2/kg2 and it is same at both the places

 

  1. Gravitational force

 

  1. No

 

  1. Kepler

 

  1. Newton