Chapterwise Physics Assignment for Class IX (Term 1)

                                                                  
                                                                       Motion (Physics)




1. Can the state of absolute rest or motion be defined for any object? Comment.
2. Name the terms used to describe the overall motion of an object.
3. Plot the following graphs:
(a)distance –time graph for an object with uniform speed
(b)distance –time graph for an object with non- uniform speed
(c)velocity –time graph for uniform motion of a car
(d)Velocity –time graph for a car moving with uniform accelerations.
(e)Velocity –time graph for a car moving with non- uniform accelerations.
(f) A body at rest
4. Is uniform circular motion of an object accelerated or not? Give reason.
5. Give an example each of a body under positive acceleration and a body under negative acceleration.
6. Name the physical quantity which (i) changes (ii) remains constant during uniform circular motion.
7. Can the average speed of a moving object be zero? Explain.
8. Can an object be accelerated if it is moving with constant speed? Justify.
9. Name two physical quantities that can be obtained from velocity – time graph.
10. A particle is moving with a uniform speed. Is it necessary that it is moving along a straight line?
11. A particle is moving with a uniform velocity. Is it necessary that it is moving along a straight line?
12. Name the physical quantities measured by (i) area under v-t graph (ii) slope of s-t graph (iii) slope of v-t graph
13. In your everyday life you came across a range of motions in which acceleration is non uniform. Identify one example of each of the type.
14. A car travels a certain distance with a speed of 50 km/h & returns with a speed of 40 km/h. Calculate (i) the average speed & (ii) average velocity of car for the whole journey.
15. A train travels 20 km at a uniform speed of 60 km/h and the next 20 km at a uniform speed of 80km/h. Calculate its average speed.
16. A car is traveling with a speed of 36km/h. the driver applies the brakes and retards the car uniformly. The car is stopped in 5s. Find (i) the retardation of the car (ii) distance traveled before it is stopped after applying the brakes.
17. A train is traveling at a speed of 72km/h. The driver applies brakes so that a Uniform acceleration of -0.2ms-2 is produced. Find the distance traveled by the train before it comes to rest.
18. A child drops a ball from a height of 10m. Assume that its velocity increases uniformly at the rate of 10m/s2 . Find (i) the velocity with which the ball strikes the ground (ii) the time taken by the ball to reach the ground.
19. A bullet moving with velocity of 10m/s is brought to rest after penetrating the wooden plank of 4 cm thickness. Calculate the acceleration of the bullet.
20. A driver of a car traveling at 52km/h applies brakes and accelerates uniformly in the opposite direction. The car stops in 5s. Plot speed-time graph and calculate the distance traveled by the car after the brakes were applied.
21. A car starts from rest and accelerates uniformly at the rate of 1m/s2 for 5s. It then maintains a constant velocity for next 30s. Then brakes are applied and the car is uniformly retarded to rest in 10s. find the maximum velocity attained by the car and the total distance traveled by it. Also plot v-t graph for the motion of the car


                                            Force & Laws of Motion (Physics)

1. A bullet fired from a gun is more dangerous than an air molecule hitting a person, though both bullet and air molecule are moving with same velocity. Explain.
2.Why are road accidents at high speeds very much worse than accidents at low speeds?.
3. What was the disbelief about the theory of motion before Newtonian motion theory? Why was it overruled?
4. When force acting on a body has an equal and opposite reaction, then why should the body move at all?
5. What can you say about the speed of a moving object if no force is acting on to it.?
6. Is a marble rolling down an inclined plane moving with constant velocity? Explain.
7. Two forces of 5N &22N are acting in a body in the same direction what will be the resultant force& in which direction will it act? If the two forces in the above example would have been acting in the opposite direction What would be the resultant force& in which direction will it act?
8.If we push the box with a small force, the box does not move, why? 9. What should be the force acting on an object moving with uniform velocity?
10. Give reasons: (a) Carpet is beaten with a stick to clean it, (b) Seat belts are provided in the cars to prevent accidents. (c) Only the carom coin at the bottom of a pile is removed when a fast moving carom coin (or striker) hits it.

Numerical

1. A200kg motorcycle is moving over a horizontal road with uniform velocity. If this motorcycle has to be stopped with a negative acceleration of 1.5m/s2 , hen what is the force of friction between the tyre of the motorcycle and the road?
2. A ball of mass 100g moving with a velocity of 0m/s is stopped by a boy in 0.2s. Calculate the force applied by the boy to stop the ball.
3. A car weighing 2400 kg and moving with a velocity of 20 m/s is stopped in 10s on applying breaks. Calculate the retardation and retarding force?
4. A car of mass 1000kg and a bus of mass 8000kg are moving with the same velocity of 36 km/h. Find the forces to stop both the car and the bus in 5s.
5. A mechanic strikes a nail with a hammer of mass 500g moving with a velocity of 20m/s The hammer comes to rest in 0.02s.after striking the nail. Calculate the force exerted by the nail on the hammer.
6. A bullet of mass 10g traveling with a velocity of 100 m/s penetrates in a wooden plank and is brought to rest in 0.01s Find (a) the distance through which the bullet penetrates in the wooden plank and (b) the force exerted on the bullet.
7. A bullet of mass 100g is fired from a gun of mass 20 kg with a velocity of 100m/s. Calculate the velocity of recoil of the gun.
8. Two bodies each of mass 1kg are moving in a straight line but opposite in direction with the same velocity of 2m/s. They collide with each other and stick to each other after collision. What is the common velocity of these bodies after collision?


                                Physics Numerical For Chapter: Gravitation

1. Calculate the gravitational force between a 10-kg ball and a 20-kg ball placed at a separation of 5 m.
2. Three balls A, B and C are kept in a straight line. The separation between A and C is 1 m, and B is placed at the midpoint between them. The masses of A, B, C are 100 g, 200 g and 300 g respectively. Find the net gravitational force on (a) A, (b) B, and (c) C.
3. A particle of mass m1 is kept at x = 0 and another of mass m2 at x = d. When a third particle is kept at x = d/4, it experiences no net gravitational force due to the two particles. Find m2/m1.
4. The acceleration due to gravity near the earth's surface is 9.8 m/s2, and the earth's radius is 6,400 km. From this data calculate the mass of the earth. Use any universal constant if required
5. Two particles of mass 200 g each are placed at a separation of 10 cm. Assume that the only forces acting on them are due to their gravitational attraction. Find the acceleration of each when they are allowed to move.
6. A particle weighs 120 N on the surface of the earth. At what height above the earth's surface will its weight be 30 N? Radius of the earth = 6,400 km.
7. Suppose the earth shrinks such that its radius decreases to half the present value. What will be the acceleration due to gravity on the surface of the earth?
8. A body weighs 120 N on the earth. Find its approximate weight on the moon.
9. Calculate the value of the acceleration due to gravity at a place 3,200 km above the surface of the earth.
10. The acceleration due to gravity at a place is 0.2 m/s 2. Find its height above the earth's surface.
11. As one moves to a place 3,200 km above the earth's surface, the acceleration due to gravity reduces to 4/9 of its value at the earth's surface. Calculate the radius of the earth from this data.
12. A ball is dropped from a cliff. Find (a) its speed 2 s after it is dropped, (b) its speed when it has fallen through 78.4 m, and (c) the time taken in falling through 78.4 m.
13. A ball is thrown upwards with a speed of 39.2 m/s. Calculate (a) the maximum height it reaches, and (b) the time taken in reaching the maximum height.
14. A ball thrown upwards takes 4 s to reach the maximum height. Find (a) the initial speed with which it was thrown, and (b) the maximum height reached.
15. An object thrown upwards reaches the highest point in 5.0 s. Find the velocity with which it was thrown.
16. A stone thrown upwards attains a maximum height of 19.6 m. Find the velocity with which it was thrown.
17. A body is thrown upwards with a velocity of 20 m/s. How much time will it take to return to its original position?
18. A ball is dropped from a height 2.50 m above the floor, (a) Find the speed v with which it reaches the floor, (b) The ball now rebounds. The speed of the ball is decreased to 3u/4 due to this collision. How high will the ball rise?
19. A ball is thrown upwards from the surface of the moon with a velocity of 19.6 m/s. (a) How much time will it take to attain the maximum height? (b) How high will it go?             
20. A flowerpot drops from the edge of the roof of a multistoried building. Calculate the time taken by the pot to cross a particular distance AB of height 2.9 m, the upper point A being 19.6 m below the roof.