Tiêu đề NEWTON'S LAWS OF MOTION & FRICTION.pdf ✅

NEET : Physics [ 260 ] www.allendigital.in  Digital BASIC QUESTION RELATED TO CONCEPT OF FORCE AND NEWTON'S LAWS OF MOTION 1. A particle is in a straight line motion with uniform velocity. A force is not required :- (1) To increase the speed (2) To decrease the speed (3) To maintain the same speed (4) To change the direction 2. Essential characteristic of equilibrium is :- (1) Momentum equals zero (2) Acceleration equals zero (3) K.E. equals zero (4) Velocity equals zero 3. When a constant force is applied to a body, it moves with uniform :- (1) Acceleration (2) Velocity (3) Speed (4) Momentum 4. A 10 kg mass is accelerated from rest to 30 m/s in 2 s. What force acts on it : - (1) 300 N (2) 150 N (3) 75 N (4) 600 N 5. A body of mass 80 g is moving with a constant velocity of 4 cm/s on a horizontal frictionless table. The force on the body (in dynes) is :- (1) Zero (2) 39200 (3) 78400 (4) 8000 6. A body of mass 6 kg moving on a horizontal surface with an initial velocity of 8 m/s comes to rest after 3 s. If one wants to keep this body moving on the same surface with a velocity of 8 m/s, the force required is :- (1) 8 N (2) 16 N (3) Zero (4) 6 N 7. An object with a mass 5 kg moves at a constant velocity of 8 m/s. A constant force then acts for 6 seconds on the object giving it a speed of 4 m/s in opposite direction. The acceleration produced is :- (1) 1.5 m/s2 (2) –2 m/s2 (3) 0.67 m/s2 (4) –0.5 m/s2 8. The velocity acquired by a mass m in travelling a certain distance d starting from rest under the action of a constant force is directly proportional to :- (1) m (2) m0 (3) 1 m (4) m 9. A ship of mass 5 × 107 kg initially at rest is pulled by a force of 25 × 104 N through a distance of 100m. Neglecting friction, the speed of the ship at this moment is : (1) 3.0 m/s (2) 1.5 m/s (3) 1 m/s (4) 2 m/s 10. A body of mass 40 gm is moving with a constant velocity of 2cm/sec on a horizontal frictionless table. The force on the table by the body is :- (1) 39200 dyne (2) 160 dyne (3) 80 dyne (4) zero 11. Three forces start acting simultaneously on a particle moving with velocity v . These forces are represented in magnitude and direction by the three sides of a triangle ABC (as shown). The particle will now move with velocity (1) less than v (2) greater than v (3) v , in the direction of largest force BC (4) v remains unchanged 12. A body with mass 5 kg is acted upon by a force F ( 3i 4j)N = − + ˆ ˆ . If its initial velocity at t = 0 is 1 u (6i 12j)ms ˆ ˆ − = − , the time at which it will just have a velocity along the Y-axis is :- (1) never (2) 10 s (3) 2 s (4) 15 s 13. When forces F1 , F2 , F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular then the particle remains stationary. If the force F1 is now removed then the acceleration of the particle is :- (1) F1/m (2) F2F3/mF1 (3) (F2 – F3)/m (4) F2/m 14. A stone of mass 1 kg is lying on the floor of a train which is accelerating with 1 ms–2. The net force acting on the stone is :- (1) zero (2) 1 N (3) 5 N (4) 10 N Exercise - I
Newton's Laws of Motion & Friction  Digital www.allendigital.in [ 261 ] 15. A car accelerates on a horizontal road due to the force exerted by :- (1) the engine of the car (2) the driver of the car (3) the car on earth (4) the road on the car MOMENTUM, IMPULSE, RATE OF CHANGE OF MOMENTUM AND AVERAGE FORCE RELATED PROBLEMS 16. Newton's II law of motion connects : (1) Momentum and acceleration (2) Change of momentum and velocity (3) Rate of change of momentum and external force (4) Rate of change of force and momentum 17. When we kick a stone, we get hurt. Due to which of the following properties of stone does it happens ? (1) Inertia (2) Velocity (3) Reaction (4) Momentum 18. A force of 20 N acts on a body of mass 10 kg for 20 seconds. The change in its momentum is (1) 40 kg-m/s (2) 100 kg-m/s (3) 400 kg-m/s (4) 200 kg-m/s 19. A player catches a ball of 100 g moving with a speed of 5 m/s. If the time taken to complete the catch is 0.25 s, the force exerted on the player's hand is :- (1) 8 N (2) 4 N (3) 2 N (4) 0 N 20. A football of mass 0.5 kg coming towards player with a velocity of 10 m/s. Player hit straight back the football with velocity 15 m/s. If the contact time is 0.02 second then the average force involved is:- (1) 250 N (2) 1250 N (3) 500 N (4) 625 N 21. A 100 g tennis ball coming at a speed of 20 m/s is hit straight back by a bat to speed of 40 m/s. The magnitude of the average force F on the ball, when it is in contact for 5 ms with the bat is:- (1) 1200 N (2) 6000 N (3) 2400 N (4) 1000 N 22. A ball weighing 50 g hits a hard surface vertically with a speed of 25 m/s and rebounds with the same speed. The ball remains in contact with the surface for 0.05 s. The average force exerted by the surface on the ball is :- (1) 100 N (2) 25 N (3) 50 N (4) 5 N 23. A tennis ball is dropped on the floor from a height of 10 m. It rebounds to a height of 5 m. The ball was in contact with the floor for 0.01 s. What was its average acceleration during the contact ? (g=10m/s2) (1) 800 m/s2 (2) 200 m/s2 (3) 1600 m/s2 (4) 2400 m/s2 24. A 150 g ball, in horizontal flight with a speed of 40 m/s, is struck by a bat. After leaving the bat, the ball travels in the opposite direction with speed 40 m/s. If the impact time for the ball-bat collision is 1.20 ms, what average force acts on the ball ? (1) 1500 N (2) 1000 N (3) 10000 N (4) 9800 N 25. n bullet strike per second elastically on a wall with speed v and rebound. What will be the force exerted on the wall by bullets if mass of each bullet is m :- (1) mnv (2) 4mnv (3) 2mnv (4) mnv 2 26. A disc of mass 2 kg is kept floating horizontally in air by firing bullets of mass 0.1 kg each vertically at it, at the rate of 5 per second. If the bullets rebound with the same speed, the speed with which these are fired will be– (1) 1·96 m/s (2) 0·98 m/s (3) 9·8 m/s (4) 19.6 m/s
NEET : Physics [ 262 ] www.allendigital.in  Digital 27. For a body of 25 kg mass, the velocity-time graph is shown in figure. The force acting on the body is : (1) 25 N (2) 50 N (3) 12.5 N (4) 100 N 28. A 2 kg toy car starts from rest (i.e. at t = 0, v = 0) can move along x-axis. Graph shows force Fx, acting on the car. The velocity of the car at t = 10 s is :- (1) 2 m/s (2) 6 m/s (3) 6.5 m/s (4) 5 m/s 29. Force-time graph for the motion of a body is shown in fig. Change in linear momentum between 0 to 8 s is :- (1) Zero (2) 4 N-s (3) 8 N-s (4) 6 N-s 30. A body of mass 2 kg has an initial speed 5 ms–1. A force acts on it for some time in the direction of motion. The force-time graph is shown in figure. The final speed of the body is :- (1) 9.25 ms–1 (2) 5 ms–1 (3) 14.3 ms–1 (4) 4.25 ms–1 31. Which one of the following statements is not true? (1) The same force for the same time causes the same change in momentum for different bodies. (2) The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts. (3) A greater opposing force is needed to stop a heavy body than a light body in the same time, if they are moving with the same speed. (4) The greater the change in the momentum in a given time, the lesser is the force that needs to be applied. 32. If force F = 50 – 20t, then impulse in interval [0, t] :- (1) 50t – 10t2 (2) 50t – 10 (3) 50 – t 2 (4) 25t2 33. In the figure given below, the position–time graph of a particle of mass 0·1 kg is shown. The impulse at t=2 sec is – (1) 0·2 kg-m/s (2) –0·2 kg-m/s (3) 0·1 kg-m/s (4) –0·4 kg-m/s 34. Gravel is dropped onto a conveyer belt at a rate of 1.5 kg/s. The extra force required in newton to keep the belt moving at 3 m/s is :- (1) 1.5 N (2) 2 N (3) 4 N (4) 4.5 N 35. A block of metal weighing 1.5 kg is resting on a frictionless plane. It is struck by a jet releasing water at a rate of 3 kg/s with a speed of 10 m/s. The initial acceleration of the block will be :- (1) 20 m/s2 (2) 5 m/s2 (3) 10 m/s2 (4) 15 m/s2 36. A block of metal weighing 2 kg is resting on a frictionless plane. It is struck by a jet releasing water at a rate of 1 kg/s and a speed of 5 m/s. The initial acceleration of the block will be :- (1) 2.5 m/s2 (2) 5 m/s2 (3) 10 m/s2 (4) 20 m/s2
Newton's Laws of Motion & Friction  Digital www.allendigital.in [ 263 ] 37. If the force on a rocket moving in force free space with an exhaust velocity of gases 400 m/sec is 300N, then the rate of combustion of the fuel, is :- (1) 1.3 kg/s (2) 0.75 kg/s (3) 2.7 kg/s (4) 0.3 kg/s 38. A satellite in force free space sweeps stationary interplanetary dust at a rate (dM/dt) = + v2. Here v is the velocity. The acceleration of satellite of mass M is :- (1) – 2 v2/M (2) – 3 v2/M (3) – v3/M (4) – v2 39. A rocket of mass 60 kg. is fired in a gravity free space is ejecting gases with velocity 300 m/s at the rate of 2 kg/s. What will be the initial acceleration of the rocket ? (1) 30 m/s2 (2) 5 m/s2 (3) 10 m/s2 (4) 15 m/s2 40. For a Rocket propulsion velocity of exhaust gases relative to rocket is 1.6 km/s. If mass of rocket system is 800 kg, then the rate of fuel consumption for a rocket to rise up with an acceleration 4.2 m/s2 will be :- (1) 12.25 kg/s (2) 17.5 kg/s (3) 7 kg/s (4) 5.2 kg/s 41. The force on a rocket, moving in gravity free space is 210 N. If the gases ejects from the rocket with speed 300 m/s (w.r.t. rocket) then the rate of combustion of the fuel is :- (1) 0.07 kg s–1 (2) 1.4 kg s–1 (3) 0.7 kg s–1 (4) 10.7 kg s–1 42. A rocket of mass 800 kg is to be projected vertically upwards. The gases are exhausted vertically downwards with velocity 40 m/s with respect to the rocket. What is the minimum rate of burning fuel, so as to just lift the rocket upwards against the gravitational attraction ? (Take g = 10 m/s2) (1) 80 kg/s (2) 400 kg/s (3) 200 kg/s (4) 800 kg/s 43. A ball is moving towards the wall as shown in diagram then the momentum of the ball is conserved (1) along the wall (2) along the normal of the wall (3) along any direction (4) Both (1) and (2) 44. A water jet, whose cross sectional area is 'a' strikes a wall making an angle '' with the wall and rebounds elastically. The velocity of water of density 'd' is v. Force exerted on wall is :- (1) 2 av2d cos (2) 2 av2d sin (3) 2 avd cos (4) avd cos FREE BODY DIAGRAM, NEWTON'S THIRD LAW 45. Which figure represents the correct F.B.D. of rod of mass m as shown in figure :- (1) (2) (3) (4) None of these 6. Working of rocket or jet is based on :- (1) Newton's law (2) Newton's II law (3) Newton's III law (4) All the three laws