How does sound travel?

How does vacuum affect sound?

How does the gravitational force between two objects depend upon the.distance between them?

Explain how sound is prodeuced by your school bell.

When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?

How does the gravitational force between two objects depend upon their masses?

A bolt of mass 0.3 kg falls from the ceiling of an elevator moving down with an uniform speed of 7 m s^-1 . It hits the floor of the elevator (length of the elevator = 3 m) and does not- rebound. What is the heat produced by the impact? Would your answer be different if the elevator were stationary?

How does the velocity of sound depend upon pressure and temperature of the medium.

Take a bucket or a bathtub. Fill it with clean water. Take a small bell in one hand. Shake this bell inside the water to produce sound. Make sure that the bell does not touch the body of the bucket or the tub. Place your ear gently on the water surface . (Be careful: the water should not enter in your ear.) Can you hear the sound of the bell? Does it indicate that sound can travel through liquids?

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.