Daily Practice Problems
Class 9 Science
Force and Laws of Motion Question 1.

What is the first law of motion?

Question 2.

Define the property of an object ‘inertia’.

Question 3.

What do you understand by the term ‘momentum’?

Question 4.

What does second law of motion state?

Question 5.

Give mathematical formulation of second law of motion.

Question 6.

What do you understand by ‘conservation of momentum’?

Question 7.

Force of friction always _________ motion of objects.

(a) opposes

(b) follows

(c) both (a) and (b)

(d) none of the above

Question 8.

What is the third law motion?

Question 9.

How do you define ‘force of one Newton’?

Question 10.

A constant force acts on an object of mass 6 kg for a duration of 3 s. It increases the object’s velocity from 4 m-s–1 to 8 m-s-1. Find the magnitude of the applied force. Now, if the force was applied for a duration of 4 s, what would be the final velocity of the object?

Question 11.

Which would require a greater force- an object accelerating with 1 ms-2 having mass 5 kg and an object accelerating with 3 ms-2 having mass 10 kg?

Question 12.

A motorcar is moving with a velocity of 90 km/h and it takes 3 s to stop after the brakes are applied. Calculate the force exerted by the brakes on the motorcar if its mass along with the passengers is 1500 kg.

Question 13.

A force of 10 N gives a mass m1, an acceleration of 15 m-s–2 and a mass m2, an acceleration of 30 m-s-2. What acceleration would it give if both the masses were tied together?

Question 14.

A bullet of mass 30 g is horizontally fired with a velocity 200 m-s-1 from a pistol of mass 3 kg. What is the recoil velocity of the pistol?

Question 15.

A girl of mass 50 kg jumps with a horizontal velocity of 6 m-s-1 onto a stationary cart with frictionless wheels. The mass of the cart is 5 kg. What is her velocity as the cart starts moving? Assume that there is no external unbalanced force working in the horizontal direction.

Question 16.

A bullet of mass 40 g is horizontally fired with a velocity 500 m-s-1 from a pistol of mass 8 kg. What is the recoil velocity of the pistol?

Question 17.

Which would require a smaller force- an object accelerating with 3 ms-2 having mass 18 kg and an object accelerating with 2 ms-2 having mass 20kg?

Question 18.

A force of 20 N gives a mass m1, an acceleration of 12 m-s–2 and a mass m2, an acceleration of 40 m-s-2. What acceleration would it give if both the masses were tied together?

Question 19.

A bullet of mass 50 g is horizontally fired with a velocity 300 m-s-1 from a pistol of mass 5 kg. What is the recoil velocity of the pistol?

Question 20.

A boy of mass 35 kg jumps with a horizontal velocity of 5 m-s-1 onto a stationary cart with frictionless wheels. The mass of the cart is 6 kg. What is his velocity as the cart starts moving? Assume that there is no external unbalanced force working in the horizontal direction.

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