Gravitation — Science STD 9 — Question

A bus running at a speed of 18km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.

A body of mass 100kg is lifted up by 10m. Find:

1. The amount of work done.
2. Potential energy of the body at that height. (value of g = 10m/s).

What is the numerical value of G and its Sl unit?

A bullet of mass 10g travelling horizontally with a velocity of 150m s^-1 strikes a stationary wooden block and comes to rest in 0.03s. Calculate the distance of penetration of the bullet into the block. Also calculate the magnitude of the force exerted by the wooden block on the bullet.

A train starting from rest moves with a uniform acceleration of 0.2m/s² for 5 minutes. Calculate the speed acquired and the distance travelled in this time.

What is a colloid? Give two examples of colloids (or colloidal solutions).

Give reason for the following observation:
The smell of hot sizzling food reaches us even from a considerable distance but to get the smell form cold food, we have to go close to it.