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1 Phone : , Kinematics Pae: 1 fo/u fopkjr Hkh# tu] uha kjehks dke] foifr ns[k NksM+s rqjar e/;e eu dj ';kea iq#"k fla ladyi dj] lrs foifr usd] ^cuk^ u NksM+s /;s; dks] j?kqcj jk[ks VsdAA jfpr% ekuo /kez iz.ksrk ln~xq# Jh j.knksm+nklth ekjkt KINEMATICS Some questions (Assertion Reason type) are ien below. Each question contains STATEMENT 1 (Assertion) and (Reason). Each question has 4 choices (A), (B), (C) and (D) out of which ONLY ONE is correct. So select the correct choice : Choices are : (A) Statement 1 is True, Statement is True; Statement is a correct explanation for Statement 1. (B) Statement 1 is True, Statement is True; Statement is NOT a correct explanation for Statement 1. (C) Statement 1 is True, Statement is False. (D) Statement 1 is False, Statement is True. 9. STATEMENT 1 The instantaneous elocity does not depend on instantaneous position ector. The instantaneous elocity and aerae elocity of a particle are always same. 10. STATEMENT 1 A man who can swim at a speed relatie to water wants to cross the rier of width d, flowin with speed u. He cannot reach a point P opposite him across the rier if u >. The time to reach the opposite point P across the rier is imainary. d u and if u > time will come out to be 11. STATEMENT 1 A balloon ascends from the surface of earth with constant speed. When it was at a heiht 50 m aboe the round, a packet is dropped from it. To an obserer on the balloon, the displacement of the packet, from the moment it is dropped to the moment it reaches the surface of earth, is 50 m. Displacement (ector) depends upon the reference frame used to measure it. 1. STATEMENT 1 If two particles, moin with constant elocities are to meet, the relatie elocity must be alon the line joinin the two particles. Relatie elocity means motion of one particle as iewed from the other. 13. STATEMENT 1 Two balls are dropped one after the other from a tall tower. The distance between them increases linearly with time (elapsed after the second ball is dropped and before the first hits round). Relatie acceleration is zero, whereas relatie elocity non zero in the aboe situation. 14. STATEMENT 1 x t raph, for a particle underoin rectilinear motion, can be as shown in the fiure.

2 Phone : , Kinematics Pae: x Infinitesimal chanes in elocity are physically possible only in infinitesimal time. 15. STATEMENT 1 When a particle moes alon a straiht line manitude of its aerae elocity is equal to its aerae speed oer any time interal. For one dimensional motion displacement and distance both are same. 16. STATEMENT 1 d is equal to d. Here has its usual meanin. dt dt If a particle is acted upon by a external force its momentum must chane. 17. STATEMENT 1 Area under elocity time raph ies displacement. Area under acceleration time raph ies elocity. 18. STATEMENT 1 When a particle is thrown obliquely from the surface of the Earth, it always moes in a parabolic path, proided the air resistance is neliible. A projectile motion is a two dimensional motion. 19. STATEMENT 1 The aerae speed and aerae elocity of the particle are different physical quantities. The aerae speed and aerae elocity hae same dimensions. 0. STATEMENT 1 Two different particles are projected horizontally with different speeds, they reach the round simultaneously. (Assumin is constant) The ertical component of the initial elocity is zero. t 1. STATEMENT 1 Two particles starts moin with elocities V 1 & V respectiely in xy plane. They can meet only if component of their elocity perpendicular to line joinin them are equal. Relatie elocity of a body w.r.t. other body is calculated alon line joinin two bodies.. STATEMENT 1 A man can cross rier of width d in minimum time t. On increasin rier elocity, minimum time to cross the rier by man will remain unchaned.

3 Phone : , Kinematics Pae: 3 Velocity of rier is perpendicular to width of rier. So time to cross the rier is independent of elocity of rier. 3. STATEMENT 1 When a body is dropped or thrown horizontally from the same heiht, it reaches the round at the same time. They hae same acceleration and same initial speed in ertical direction. 4. STATEMENT 1 : The maximum rane alon the inclined plane, when thrown downward is reater than that when thrown upward alon the same inclined plane with constant elocity. : The maximum rane alon inclined plane is independent of anle of inclination. 5. STATEMENT 1 : If particle is moin in straiht line with constant acceleration or retardation its elocity may be zero at particular instant. : If particle moes alon a straiht line it may be accelerated, decelerated or can moe with a constant elocity. 6. STATEMENT 1 : In uniform circular motion acceleration is constant. : In uniform circular motion manitude of acceleration is the centre. V r and direction is always towards 7. STATEMENT 1 : A particle is projected at an anle θ ( < 90) to horizontal, with a elocity u. When particle strikes the round its speed is aain u. : Velocity alon horizontal direction remains same but elocity alon ertical direction is chaned. When particle strikes the round, manitude of final ertical elocity is equal to manitude of initial ertical elocity. 8. STATEMENT 1 : Two particles of different mass, projected with same elocity at same anles. The maximum heiht attained by both the particles will be same. : The maximum heiht of projectile is independent of particle mass 9. STATEMENT 1 : When a particle moes in a circle with a uniform speed, its elocity and acceleration both chanes. : The centripetal acceleration in circular motion is dependent on anular elocity of the body. 30. STATEMENT 1 : The net acceleration of a particle in circular motion is always directed radially inward. : Wheneer a particle moes in a circular path an acceleration exists which is directed towards the centre. 31 STATEMENT 1 : A coin is allowed to fall in a train moin with constant elocity. Its trajectory is parabola as seen by obserer attached to the train. : An obserer on round will see the path of coin as a parabola. 3. STATEMENT 1 : In a projectile motion from round R=H at θ = tan 1 (4). 1 : Max rane of projectile is proportional to (elocity) and. 33. STATEMENT 1 : When speed of projection of a body is made n-times, its time of fliht becomes n times. : This is because rane of projectile become n times. 34. STATEMENT 1 : In a uniformly accelerated motion, acceleration time raph is straiht line with positie slope. : Acceleration is rate of chane of elocity.

4 Phone : , Kinematics Pae: STATEMENT 1 : Horizontal elocity in projectile motion remains constant. :Acceleration due to raity is ertical. 36. STATEMENT 1 : In uniform circular motion acceleration is constant. : In uniform circular motion speed is constant. 37. STATEMENT 1 : A particle is moin on a horizontal surface. Its path will be straiht line if initial elocity and acceleration are alon same horizontal surface. : Anle between u and a determine path therefore, it may be accelerated or retarded curilinear. 38. STATEMENT 1 : If air resistance is considered then time of ascent and time of descent will be different. : Manitudes of acceleration will be different in upwards and downward motion. 39. STATEMENT 1 : For maximum heiht H of a projectile when the maximum rane is R the only alid relation is that H is 50% of R. u sin θ u sin θ : R = and H =. 40. STATEMENT 1 :A particle in motion may not hae ariable speed but constant elocity. : A particle hain non zero acceleration may moe with constant speed. 41. STATEMENT 1 : A body, whateer its motion, is always at rest in a frame of reference which is fixed to the body itself. : The relatie elocity of a body with respect to itself is zero. 4. STATEMENT 1 : A body hain non zero acceleration can hae a constant elocity. : Acceleration is the rate of chane of elocity. 43. STATEMENT 1 : Durin a turn, the alue of centripetal force should be less than the limitin frictional force. : The centripetal force is proided by the frictional force between the tyre and the road. Hint & Solution 9. (C) 10. (A) 11. (D) 1. (A) 13. (A) 14. (D) 15. Both statements are false. 16. (D) 17. (C) 18. (D) 19. (B) 0. (A) 1. (C). (A) 3. (A) 4. (C) 5. (B) 6. (D) 7. (A) 8. (A) 9. (B) 30. (D) 31. (D) 3. (B) 33. (C) 34. (D) 35. (A) 36. (D) 37. (D) 38. (A) 39. (A) 40. (B) 41. (A) 4. (D) 43. (A) d s 9. As =, hence statement 1 is correct. dt Instantaneous elocity is same always to aerae elocity if the particle is moin with constant elocity. 10. Time to cross the rier t = d u.

5 Phone : , Kinematics Pae: 5 u P 11. To an obserer on the balloon, the round is moin. d 1. Suppose motion of 1 is iewed from then as is stationary. If 1 is to meet it, it 1 must come straiht towards i.e., the relatie elocity must be alon At the hih point of the raph elocity (slope of x t cure) chares suddenly from a positie to a neatie alue. This is physically impossible. A - u 17. Area under acceleration time raph ies chane in elocity and not elocity. 18. The particle will moe in a parabolic path till acceleration (due to raity) is constant. For this the particle should be near the surface of the Earth and air resistance should be neliible. 6. In uniform circular motion direction of acceleration is always alon the radial direction. As particle is rotatin so radial ector keeps on chanin. 7. U x = 0, a x = 0 V x = U x + a x T = U x U y = u sin θ; a y = V y = u sin θ t u sin θ = u sin θ. ; V y = u sin θ. 8. u sin θ H = i.e., it is independent of mass of projectile. 9. In uniform circular motion, the manitude of elocity and acceleration remains same, but due to chane in direction of motion, the direction of elocity and acceleration chanes. Also the centripetal acceleration is ien by a = ω r. 30. In case of non uniform circular motion, net acceleration will not be directed towards centre. 31. For the obserer attached with train, the initial horizontal elocity of coin and train are same, thus obserer will find its path as a straiht line. u sin θ 3. Use R = Rane in a function of θ also. u sin θ nu sin θ 33. As T = T = T = nt R = u cosθt R = nu cos θ.nt R = n R 34. Positie slope indicates that acceleration increases uniformly with time. It is not uniform. 35. Since no force is present as horizontal direction elocity of constant. 36. Direction of acceleration chanes. 37.

6 Phone : , Kinematics Pae: 6 a a u accelerated curilinear u retarded curilinear a u straiht line. 38. F(air resistance) m Motion Motion F(air resistance) m 39. Because R max u = [for θ = 45º] u and Hmax = H max can be 50% of rane. 41. A body has no relatie motion with respect to itself. Hence if a frame of reference of the body is fixed, then the bodies will be always at relatiely rest in this frame of reference. So a is correct. dν 4. Acceleration is the rate of chane of elocity i.e., a = dt 43. If the alue of frictional force µm is less than centripetal force, then it is not possible for a ehicle to take twin and the bicycle would take a oer turn. Thus condition for no oer turnin is mν µ m r So statement I and statement II are correct and statement II is the correct explanation of statement I. Hence (a) is correct.