Universal Law of Gravitation | Gravitation | Assessment | English | Grade 9

What is the SI unit of universal gravitational constant?

• N m²/kg²

• N m²/kg

• N m/kg²

• Newton

Answer explanation

SI unit of universal gravitational constant is N m²/kg²

Tags

NGSS.HS-PS2-4

Suppose force between two bodies is F. If the distance between them gets multiplied by 4, what will be the new force between them?

• F/ 25 N

• F/ 4 N

• F/ 8 N

• F/ 16 N

Answer explanation

Force is inversely proportional to the square of the distance, so if distance is multiplied by 4, force becomes F/ 16 N.

Tags

NGSS.HS-PS2-4

Gravitational force between two objects are 400 N. If the mass of the two bodies is reduced to half, what will the force between them?

• 400 N

• 200 N

• 100 N

• None of these

Answer explanation

F = 400 N If mass is halved, force becomes F = 400 /4 = 100 N

Tags

NGSS.HS-PS2-4

The distance of earth from moon is 3 × 10^5 km and from sun is 1.5× 10^8 km. The mass of earth, moon and sun are 6 x 10^24 kg, 7 x 10^22 kg and 2 × 10^30 kg respectively. In which case is more force exerted by earth?

• Force exerted by earth on moon is more

• Force exerted by earth on sun is more

• Same force is exerted by earth on sun and moon

• Given data is insufficient

Answer explanation

Let constant of proportionality be G We know, F = G (M × m)⁄ d² Force exerted by earth on moon = G(6 x 10^24 × 7 x 10^22 kg)⁄( 3 × 10^5 km)² = G(6 x 10^24 × 7 x 10^22 kg)⁄( 9 × 10^10 km) = G × 4.66 × 10^36 Force exerted by earth on sun F = G (M × m)⁄ d² = G(6 x 10^24 × 2 × 10^30 kg)⁄( 1.5× 10^8 km)² = G(6 x 10^24 × 2 × 10^30 kg)⁄( 2.25× 10^16 km)² = G × 5.33 × 10^38 Hence, force exerted by earth on sun is more. Option 2 is correct

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-4

Tides in the ocean is caused by ____.

• Gravitational pull of the moon on earth

• Gravitational pull of the sun on earth

• Gravitational pull of earth on the sun and the moon.

• Both options 1 and 2

Answer explanation

Tides in the ocean is caused by gravitational pull of the sun and the moon.

Tags

NGSS.HS-PS2-4

A spherical object with mass 200 kg is in contact with another spherical object with twice its mass and equal dimension. Calculate the force between them if radius of the object is 50m. Take G as 6 ×10⁻¹⁰ N m²/kg²

• 53.36 x 10^-11 N

• 106.7 x 10^-11 N

• 53.36 x 10^11 N

• 106.7 x 10^11 N

Answer explanation

M1= 400kg, M2= 200kg Distance = 50 × 2 = 100m G = 6.67 ×10^-11 N m²/kg² F = 6.67 ×10^-11 N m²/kg² × 400 kg × 200 kg⁄ (100)² = 53.36 × 10^-11 N

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-4