Newtons Laws Of Motion Numericals 4s4ba

IX CBSE PHYSICS Force and Laws of Motion Numericals 1. If a net horizontal force of 130 N is applied to a person with mass 60.0 kg who is resting on the edge of a swimming pool, what horizontal acceleration is produced? [2.2 m/s2 ] 2

2. What net force is required to accelerate a car at a rate of 2 m/s if the car has a mass of 3,000 kg? 2

3. Sally has a car that accelerates at 5 m/s . If the car has a mass of 1000 kg, how much force does the car produce? 4. What magnitude of net force is required to give a 135 kg refrigerator an acceleration of magnitude 1.40 m/s2. [189 N] 5. A box rests on a frozen pond, which serves as a frictionless horizontal surface. If a fisherman applies a horizontal force with magnitude 48.0 N to the box and produces an acceleration of magnitude 3.00 m/s2, what is the mass of the box? [16.0 kg] 6. A crate with mass 32.5 kg initially at rest on a warehouse floor is acted on by a net horizontal force of 140 N.What acceleration is produced? How far does the crate travel in 10.0 s? What is its speed at the end of 10.0 s? [4.31 m/s2, 215 m, 43.1 m/s] 7. At the surface of Jupiter’s moon Io, the acceleration due to gravity is g = 1.81 m/s2. A watermelon weights 44.0 N at the surface of the earth. What is the mass on the earth’s surface? What are its mass and weight on the surface of Io? [4.49 kg, 4.49 kg, 8.13 N] 8. A .22 rifle bullet, traveling at 350 m/s, strikes a block of soft wood, which it penetrates to a depth of 0.130 m. The block of wood is clamped in place and doesn’t move. The mass of the bullet is 1.80 g. Assume a constant retarding force. How much time is required for the bullet to stop? What force, in newton, does the wood exert on the bullet? 9. A body with a mass of 1.0 kg is accelerated by a force F = 2.0 N. What is velocity of this body after 5.0 s of motion? 10. A force of 15 N acts for 5s on a body of mass 5Kg which is initially at rest. Calculate.a) final velocity of the body b) the displacement of the body 11. A scooter is moving with a velocity of 20m/s when brakes are applied. The mass of the scooter and the rider is 180Kg. the constant force applied by the brakes is 500N. a) How long should the brakes be applied to make the scooter comes to a halt? b) How far does the scooter travel before it comes to rest? 12. A car of mass m=1200 kg is traveling at a speed of 50km/h. Suddenly the brakes are applied and the car is brought to a stop over a distance of 20m. Assuming constant breaking force find: a. the magnitude of the breaking force, b. the time required to stop.

c. What will be the stopping distance if the initial speed is 100km/h? 13. How much force is needed to accelerate a trolley of mass 20 g through 1 m/s2. 14. A force of 100N acts on a mass of 25 kg for 5 s .What velocity does it generate? 15. A bullet leaves a rifle with a velocity of 100m/s and the rifle of mass 2.5 kg recoils with a velocity of 1m/s. Find the mass of the bullet? 16. A certain force acting on a mass of 15kg for 3s, gives it a velocity of 2m/s. Find the magnitude of force. 17. A cricket ball of mass 0.15 kg is moving with a velocity of 1.2m/s. Find the impulse on the ball and average force applied by the player if he is able to stop the ball in 0.18s. 18. A motor car of mass 200kg is moving with a certain velocity. It is brought to rest by the application of brakes, within a distance of 20m when the average resistance being offered to it is 500N.What was the velocity of the motor car? 19. A body of mass 0.5kg undergoes a change of velocity of 4cm/s in 4s What is the force acting on it? 20. A force of 8N acting on an 8kg mass for 4s provides its some velocity. Calculate the velocity. 21. What would be the weight of a body of mass 50kg on the surface of the moon, where g = 1.6m/s2 what would be its mass? 22. A boy jumps a distance of 2m on the surface of the earth. What distance will he jump on the surface of the moon where g is 1/6th of the value on the surface of the earth? 23. Two bodies of mass 1kg and 2 kg moving in the direction opposite to each other with a speed 5m/s collide. Calculate the total momentum of the system before collision. 24. A bullet of mass 15g leaves the barrel of a gun with a velocity of 120m/s.The gun recoils with a velocity of 1m/s. find the mass of the gun. 25. A force of 3N acts on a mass of 0.5kg at rest for 10s. Find the final velocity and the momentum of the body after 10s. 26. A force of 80N acting on a certain mass for 3s gives it a velocity of 6m/s. find the mass of the body if the body was initially at rest. 27. A car of mass 200 kg moving at 36 km/h is brought to rest after it covered a distance of 10 m. Find the retarding force acting on the car. 28. The figure below show a velocity time graph for a scooterist having a total mass of 150 kg. From the graph calculate - a) The acceleration in first 4 seconds b) The distance covered in the first 4 seconds. c) The force acting in the first 4 seconds.

29. A certain force exerted for 1.2 seconds raises the speed of an object from 1.8 m/s to 4.2 m/s. Later the same force is applied for 2 seconds. How much does the velocity change in 2 seconds?