Problem Statement 64) The time period of a simple pendulum is 2 s. What is its frequency ? What name is given to such a pendulum ? Solution f = 1/T = ½ Hz = 0.5 Hz Time period is 2 sec => That means it’s a seconds’ pendulum 65) A seconds’ pendulum is taken […]

## Solution to problems – class 9 – Set 1 Q 60

Problem Statement 60) A metallic sphere of mass 2 kg and volume 2.5 x 10-4 m3 is completely immersed in water. Find the buoyant force exerted by water on the sphere. Density of water = 1000 kg/m3 Solution Volume of the water displaced = volume of the completely immersed sphere=2.5 x 10-4 m3 Mass of […]

## Solution to problems – class 9 – Set 1 Q 59

Problem Statement 59) A man wearing a bullet-proof vest stands still on roller skates. The total mass is 80 kg. A bullet of mass 20 grams is fired at 400 m/s. It is stopped by the vest and falls to the ground. What is then the velocity of the man ? Solution When both man […]

## Solution to problems – class 9 – Set 1 Q 58

Problem Statement 58) A heavy car A of mass 2000 kg travelling at 10 m/s has a head-on collision with a sports car B of mass 500 kg. If both cars stop dead on colliding, what was the velocity of car B ? Solution Say, velocity of B before collision be V m/s Initial momentum […]