CBSE Guess > Papers > Important Questions > Class XII > 2010 > Physics > Physics By Ajay Yadav CBSE CLASS XII
Q. 20. on arainy day , the rain was falling vertically with a speed of 30 m/s . if the wind starts flowing with a speed of 10 m/s in the direction from north to south , find the direction in which the boy should hold his umbrella in order to protect himself from the rain . [180 with the vertical ] Q. 21. a water tap leaks that water drops fall at regular intervals . tap is fixed 5 m above the ground . first drop reaches ground and at that very instant third drop leaves the tap . what is the height of the second drop at that instant ? [ 3.75 m ] Q. 22. a man standing on a road has to hold his umbrella at 300 with the vertical to keep the rain away . he throws the umbrella and starts running at 10km/h .he finds that raindrops are hitting his head vertically . find the speed of raindrops with respect to (a) the road (b) the moving man [20 km/h , 10√3 km/h ] Q. 23. a police van moving on a highway with a speed of 30 km/h fires a bullet at a thief’s a car speeding away in the same direction with a speed of 192 km/h . if the muzzle speed of the bullet is 150 m/s , with what speed does the bullet hits the thief’s car ? [ 105 m/s ] Q. 24. a man can swim at a speed of 3 km/h in still water . he wants to cross a 500 m wide river flowing at 2 km/h . he keeps himself always at an angle of 1200 with the river flow while swimming ?(a) find the time he takes to cross the river (b) at what point on the opposite bank will he arrive ? [1/3√3 h , 1/6√3 km ] Q. 25. on a two- lane road , car A is travelling with a speed of 36 km/h . two cars B and c approach car A from opposite direction with speed of 54 km/h each . at a certain instant , when the distance AB equal to AC , both being 1 km , B decides to overtake A before C does . what minimum acceleration is required to avoid an accident . [ 1 m/s2] Q. 26. a particle starts from rest with a constant acceleration . at a time t second , the speed is found to be 100 m/s and one second later the speed becomes 150 m/s . find (a) the acceleration and (b) the distance travelled during the (t+1)th second [50 m/s2 , 125 m ] Q. 27. a freely falling particle from a height h covers h/2 in last second of its motion . show that height Q. 28. a particle moves in the x-y plane with a constant acceleration of 1.5 m/s2 in the direction making an angle of 370 with the x-axis . at t=0 the particle is at the origin and its velocity is 8 m/s along the x axis . find the velocity and the position of the particle at t=4.0 s [ 41.6 m , 7.2 m , 4 sec. ] Q. 29. an air craft is flying at a height 3400 m above the ground . if the angle subtended at ground observation point by the aircraft positions 10 sec apart is 300 , what is the speed of aircraft . [ 182.2 m/s ] Q. 30. in a harbour , wind is blowing at he speed of 72 km/h and the flag on the mast of a boat anchored in the harbour flutters along N-e direction . if the boat starts moving at a sped of 51 km/h to the north , what is the direction of flag on the mast of the boat ? [ 450] Q. 31. a machine gun is mounted on the top of a tower 100 m high . at what angle should the gun be inclined to cover a maximum range of firing on the ground below ? the muzzle speed of bullet is 150 m/s . take g=10 m/s2 [ 43.80 ] Q. 32. a mass m is moved on a frictionless plane by a string moving with velocity v as shown in the figure . what is the horizontal velocity of the mass ? [v/sinƟ ] Q. 33. two cars are moving with same velocity of 30 km/h maintaining a distance of 5 km between them . find the speed of third car moving in the opposite direction and meeting the two cars at an interval of 240 sec .[45km/h] Q. 34. a ball thrown vertically upwards with a speed of 19.6 m/s from the top of a tower returns to the earth in 6 seconds . find the height of tower . ([58.8 m ] Q. 35. a juggler maintain four balls in motion , making each of them rise to a height of 20 m from his hand . what time interval should be maintain , for the proper distance them ? [ 1sec.] Q. 36. a body falling from rest was observed to fall through 78.4 m in 2 seconds . find how long had it been falling before it was observed ? [3 sec. ] Q. 37. determine the horizontal force required to displace a mass of 0.03 kg suspended by a string until the string makes an angle 300 with the vertical . [ 0.01732 kgf ] Q. 38. a bird flies north at 20 m/s for 15 sec. it rests for 5 sec. and then flies south at 25 m/s for 10 sec. for the whole trip , find (a) rhe average speed (b) the average velocity (c) the average acceleration[ 18.34 m/s,1.67 m/s, -1.5 m/s2] Q. 39. a particle goes along a quadrant AB of a circle of radius 5 cm with a constant speed 2.5 m/s as shown . find the average velocity and average acceleration over the interval AB. [2.252 m/s , 1.126 cm/s2] Q. 40. a ball is thrown up from the ground reaches a maximum height of 20 m .find its initial velocity , the time taken to reach the highest point , its velocity just before hitting the ground , its displacement between 0.5 sec and 2.5 sec., the time at which it is 15 m above the ground . [ 20 m/s , 2s, -20m/s , 10m ,1s] Q. 41. a ballon starting from the ground has been ascending vertically at a uniform velocity for 4 sec and a stone let fall from it reaches the ground in 6 sec . find the velocity of the balloon and its height when the stone was let fall .( g=10 m/s2) [ 72 m , 42 m/s downward ) Q. 42. a car starts from rest and acceleration uniformly for 10 sec to a velocity of 8 m/s . it then run at a constant velocity and is finally brought to rest in 64 m with a constant retardation . the total distance covered by the car is 584 m . find the value of acceleration , retardation and total time taken .
Paper By Mr. Ajay Yadav |
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