Force and Laws of Motion — Science STD 9 — Question

A force of 50N acts on a body and moves it a distance of 4m on a horizontal surface. Calculate the work done if the direction of force is at an angle of 60° to the horizontal surface.

Which of the following are physical changes and which are chemical changes?
Burning of candle wax, Melting of candle wax, Mixing of iron filings and sand, Burning of wood, Breaking a piece of chalk, Burning a piece of paper, Cutting a piece of paper.

Define the term 'work'. Write the formula for the work done on a body when a force acts on the body in the direction of its displacement. Give the meaning of each symbol which occurs in the formula.

Explain why, the motion of a body which is moving with constant speed in a circular path is said to be accelerated.

What is sound? What type of waves are sound waves in air?

Draw a velocity-time graph to show the following motion:
A car accelerates uniformly from rest for 5s ; then it travels at a steady’ velocity for 5s.

Through which of the following materials can sound travel?
Wood, air, water, sream, ice, hydrogen, steel, diamond.

What is a molecule? Explain with an example.

What are cathode rays? What is the nature of charge on cathode rays?

How fast should a man of 50kg run so that his kinetic energy be 625J?