NCERT SOLUTION CLASS 9 PHYSICS- GRAVITATION CHAPTER 10

QUESTION-11

Why does a sheet of paper fall slower than one crumpled into a ball?

SOLUTION:

Because of the effect of air resistance, Air resistance (force exerted by air) acts in the direction of the object's motion.

The magnitude of air resistance is determined by the shape and area of the object, as well as the density and viscosity of the air.

In the case of a sheet of a paper, greater air resistance due to the larger surface area slows the fall.

In the case of a crumpled paper ball, lower air resistance due to smaller surface area allows it to fall faster.

QUESTION-14

A stone is released from the top of a tower of height 19.6 m.Calculate its final velocity just before touching the ground.

SOLUTION:

QUESTION-15

A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

SOLUTION:

QUESTION-16

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.

SOLUTION:

QUESTION-18

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.

SOLUTION: