English Medium कक्षा ९ - CBSE Question Bank Solutions

A trolley, while going down an inclined plane, has an acceleration of 2 cm s⁻². What will be its velocity 3 s after the start?

A racing car has a uniform acceleration of 4 m s⁻². What distance will it cover in 10 s after start?

A stone is thrown in a vertically upward direction with a velocity of 5 m s^-1. If the acceleration of the stone during its motion is 10 m s^-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m s⁻², with what velocity will it strike the ground? After what time will it strike the ground?

An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.

If action is always equal to the reaction, explain how a horse can pull a cart.

Explain, why is it difficult for a fireman to hold a hose, which ejects large amounts of water at a high velocity.

A stone of 1 kg is thrown with a velocity of 20 m s⁻¹ across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. What is the force of friction between the stone and the ice?

Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?

According to the third law of motion, when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.

What is power?

Define 1 watt of power.

A lamp consumes 1000 J of electrical energy in 10 s. What is its power?

Define average power.

A battery lights a bulb. Describe the energy changes involved in the process.

What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.

An electric heater is rated 1500 W. How much energy does it use in 10 hours?

Find the energy in joules consumed in 10 hours by four devices of power 500 W each.

Is the following statement true or false :
A rocket can propel itself in a vacuum.