PHYSICS Force & Laws of Motion Assignment Class 9 CBSE

CLASS: IX

PHYSICS ASSIGNMENT CH: 9 FORCE AND LAWS OF MOTION

Q.1 Answer the following questions: 1.The law that defines force and inertia is (a) Newton’s first law (b) Newton’s second law (c) Newton’s third law (d) None of the above 2. Inertia of a body in linear motion is measured by (a) velocity (b) Momemtum (c) Mass (d) Force 3. Newton’s second law of motion gives us (a) definition of inertia (b) definition of force (c) measure of force (d) None of the above 4. Recoil velocity of gun is (a) equal to velocity of bullet (b) much greater than velocity of bullet (c) much smaller than velocity of bullet (d) None of the above Q.2 Give reasons for the following: 1.Wearing the seat belt reduces the possibility of injury during an automobile accident. 2.A passenger jumping out of a moving train falls forward. 3.An athlete runs a distance before taking a leap in the high jump. 4.Jumping on a cemented floor causes more injury than on a heap of sand. 5.Karate player can break a pile of tiles with a single blow of his hand. 6. Mud guards are used in vehicles. Q.3 Solve the following numericals: 1. A constant retarding force of 200N is acting on a body of mass 50 kg moving initially with the speed of 20 m/s. How long does the body take to stop? 2. What will be the change in acceleration of a sliding block, if its mass is doubled while a constant force is acting on it? 3. A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer? 4. A of mass 1500 kg travelling at 25 m/s collides with another car B of mass 1000 kg travelling at 15 m/s in the same direction. After the collision the velocity of car A becomes 20 m/s. Calculate the velocity of car B after the collision.