English Medium Class 9 - CBSE Question Bank Solutions for Science

State whether the following statement is true or false :
Unbalanced forces acting on a body change its shape.

State whether force is a scalar or a vector quantity?

Fill in the following blank with suitable word:

When a running car stops suddenly, the passengers are jerked …………………..

Fill in the following blank with suitable word :

When a stationary car starts suddenly, the passengers are jerked …………………..

Fill in the following blanks with suitable word :

If there were no unbalanced force of……………….. and no…………………. resistance, a moving bicycle would go on moving for ever.

Which of the two, balanced forces or unbalanced forces, can change the shape of an object ? Give an example to illustrate your answer.

Give reason for the following :
When a hanging carpet is beaten with a stick, the dust particles start coming out of it.

Explain why, it is dangerous to jump out of a moving bus.

State the various effects of force.

Give one example  where  a force moves a stationary body.

Give one example where a force stops a moving body.

Give one example where a force changes the speed of a moving body.

Give one example  where a force changes the direction of a moving body.

Give one example where a force changes the shape (and size) of a body.

What do you understand by the terms “balanced forces” and “unbalanced forces” ? Explain with examples.

What type of forces – balanced or unbalanced – act on a rubber ball when we press it between our hands ? What effect is produced in the ball ?

What happens to the passengers travelling in a bus when the bus takes a sharp turn ? Give reasons for your answer.

Why are road accidents at high speeds very much worse than road accidents at low speeds ?

A car is moving on a level road. If the driver turns off the engine of the car, the car’s speed decreases gradually and ultimately it comes to a stop. A student says that two forces act on the car which bring it to a stop. What could these forces be ? Which of these two forces contributes more to slow down and stop the car ?

There are two types of forces X and Y. The forces belonging to type X can produce motion in a stationary object but cannot change the shape of the object. On the other hand, forces belonging to type Y cannot produce motion in a stationary object but can change the object. What is the general name of the forces as (a) X, and (b) Y?