English Medium Class 9 - CBSE Question Bank Solutions

A bus starting from rest moves with a uniform acceleration of 0.1 m s^-2 for 2 minutes. Find

1. the speed acquired
2. the distance travelled.

A train is travelling at a speed of 90 km h⁻¹. Brakes are applied so as to produce a uniform acceleration of −0.5 m s⁻². Find how far the train will go before it is brought to rest.

A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 3.0 m s⁻² for 8.0 s. How far does the boat travel during this time?

From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s⁻¹. Calculate the initial recoil velocity of the rifle.

Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s⁻¹ and 1 m s⁻¹, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s⁻¹. Determine the velocity of the second object.

Two objects, each of mass 1.5 kg are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s⁻¹ before the collision during which they stick together. What will be the velocity of the combined object after collision?

A hockey ball of mass 200 g travelling at 10 m s⁻¹ is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s⁻¹. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.

An object of mass 1 kg travelling in a straight line with a velocity of 10 ms⁻¹ collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.

Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions.

What is the audible range of the average human ear?

What is the range of frequencies associated with infrasound?

What is the range of frequencies associated with ultrasound?

A person has a hearing range from 20 Hz to 20 kHz. What are the typical wavelengths of sound waves in air corresponding to these two frequencies? Take the speed of sound in air as 344 m s⁻¹.

Name the physical quantity which is considered to be a measure of the quantity of motion of a body.

What is the SI unit of momentum ?

state whether momentum is scalar or vector.

What is the total momentum of the bullet and the gun before firing ?

Name the physical quantity whose unit is kg.m/s.

Explain why, it is easier to stop a tennis ball than a cricket ball moving with the same speed.

Explain the meaning of the following equation : .
p = m x v
where symbols have their usual meanings.