Gravitation — Science STD 9 — Question

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

Give one example of the diffusion of a solid in another solid.

Giving reasons state the reading on a spring balance when it is attached to a floating block of wood which weighs 50g in air.

How does applying pressure (or compression) help in the liquefaction of a gas?

When you step ashore from a stationary boat, it tends to leave the shore. Give reason.

Which postulate of Dalton’s atomic theory can explain the law of conservation of mass?

Arrange the following speeds in increasing order (keeping the least speed first):

1. An athlete running with a speed of 10m/s.
2. A bicycle moving with a speed of 200m/min.
3. A scooter moving with a speed of 30km/h.

Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?