Give reasons :
When a bottle containing mustard seeds shaken vigorously, the seeds move away from each other and stick to the bottle.

Two aeroplanes A and B, each moving with a speed of 720 km/hour, are moving directly away from each other. Aeroplane A emits a whistle of frequency 1080 Hz. The apparent frequency heard by a person in plane B will be (velocity of sound in air = 340 m//s )

State the expression for apparent frequency : i. when source of sound and listener are moving away from each other.

Give scientific reasons : When a burning stick of incense is moved fast in a circle , a circle of red light is seen.

Give reasons : As the sound wave propagates from one place to the other in air, the air itself is not required to move from one place to the other.

Give scientific reasons: An ordinary glass bottle cracks when boiling water is poured into it.but a borosil glass bottle does not.

A point particle of mass m, moves long the uniformly rough track PQR as shown in figure. The coefficient of friction, between the particle and the rough track equals mu . The particle is released, from rest from the point P and it comes to rest at a point R. The energies, lost by the ball, over the parts, PQ and QR, of the track, are equal to each other, and no energy is lost when particle changes direction from PQ to QR. The value of the coefficient of friction mu and the distance x (=QR) , are, respectively close to:

Write the given information as an equation and find its solution : Sakshl prepared some jam at home and filled it in bottles. After giving away 7 of the bottles to her friends she still has 12 for herself. How many bottles had she made in all ? If she filled 250 g of jam in each bottle, what was the total weight of the jam she prepared ?

Give scientific reasons for the following: Dust and other small particles are attached by a plastic comb which has been moved vigorously through dry hair.

Give scientific reasons: A plastic bottle , completely filled with water, when kept in a freezer, is likely to break.