Untitled Document

Question Bank No: 1

1. The angular speed of hour's hand of a watch is

a)		$\frac{π}{60 \times 60}$ rad/s
b)		$\frac{2 π}{60 \times 60}$ rad/s
c)		$\frac{π}{12 \times 60 \times 60}$ rad/s
d)		$\frac{π}{60 \times 60 \times 60}$ rad/s

2. Find the minimum speed of a bike at highest point of a globe of diameter 19.6 m?

a)		9.8 m/s
b)		19.6 m/s
c)		4.9 m/s
d)		39.2 m/s

3. A curved road of diameter 1.8 is banked ,so that no friction is required at a speed of 30 m/s.What is the banking of angle.

a)		$6^{0}$
b)		$16^{0}$
c)		$26^{0}$
d)		$0. 6^{0}$

4. If the radius of the circular path particle going around the circle is doubled without changing its frequency of rotation. Then centripetal force on it is

a)		unchanged
b)		doubled
c)		halved
d)		quadrapted

5. The K.E. of a body rotating with an angular speed w, depends

a)		distribution of mass
b)		angular speed
c)		both a and b
d)		neither (a) nor (b)

6. A car takes a turn around a circular curve of it turns at double the speed ,the tendency to over turn is

a)		halved
b)		doubled
c)		quadrapted
d)		unchange

7. A man is riding on a cycle with velocity 7.2 km/hr up a hill having a slope l in 20. Total mass of the man and cycle is 100kg. The power of man is

a)		98 W
b)		49 W
c)		196 W
d)		147 W

8. A body is moving under the action of force, suddenly force is incresed to such an extent that its K.E is increased by 100%. The momentum increased by

a)		100%
b)		60%
c)		40%
d)		20%

9. If a hockey stick slides on a perfectly frictionless surface, it will eventually slow down because of its inertia. State whether the statement

a)		is true
b)		is false
c)		may be true or false
d)		is incomplete

10. A vector $\vec{F_{1}}$ acts along +ve x-axis if its vector product with another vector $\vec{F_{2}}$ is zero, then $\vec{F_{2}}$ could be

a)		4 $\hat{j}$
b)		-( $\hat{i} + \hat{j}$ )
c)		( $\hat{j} + \hat{k}$ )
d)		-4 $\hat{i}$

11. A rain drop of mass 1mgm is falling with uniform speed 0.1 m/s. The net weight of the drop is

a)		zero
b)		$10^{- 5}$ N
c)		$10^{- 3}$ N
d)		$10^{- 6}$ N

12. The angle between the vectors $\vec{A}$ and $\vec{B}$ is $θ$ . The value of triple product $\vec{A}$ . $\vec{B}$ $\times \vec{A}$ is

a)		$A^{2} B$
b)		$A^{2} B$ sin $θ$
c)		$A^{2} B$ cos $θ$
d)		zero

13. When a force F acts on a body of mass m, the acceleration produced in the body is a. If three equal forces $F_{1}$ = $F_{2}$ = $F_{3}$ =F act on the same body as shown in fig. The acceleration produced is
lawsofmotionQ20

a)		$(\sqrt{2} - 1)$ a
b)		( $\sqrt{2}$ +1) a
c)		$\sqrt{2}$ a
d)		2a

14. A body projected along an inclined planed of angle of inclination $30^{\circ}$ stops after covering a distance $x_{1}$ . The same body projected with the same speed stops after covering a distance $x_{2}$ . If the angle of inclination is increased to $60^{\circ}$ , the ration $\frac{x_{1}}{x_{2}}$ is

a)		1
b)		$\sqrt{3}$
c)		2
d)		$\sqrt{2}$

15. In Fig a block A is released from rest when spring is at its natural un stretched length. For block B of mass M to leave contact with the ground at some stage, the minimum mass of A must be
lawsofmotionQ18

a)		2M
b)		M/2
c)		M
d)		Cannot say

16. A book is lying on the table. What is the angle between the action of the book on the table and the reaction of the table on the book.

a)		$0^{\circ}$
b)		$30^{\circ}$
c)		$90^{\circ}$
d)		$180^{\circ}$

17. A cyclist moving in a circular track of radius 80m with a velocity v = 36 km/ hr. He have to lean from the vertical approximately through an angle ( g=10 m/ $s^{2}$ )

a)		$\tan^{- 1}$ (4)
b)		$\tan^{- 1}$ $(\frac{1}{8})$
c)		$\tan^{- 1}$ $(\frac{1}{4})$
d)		$\tan^{- 1}$ (2)

18. Three forces start acting simultaneously, on a particle moving with velocity $\vec{v}$ . These forces are represented in magnitude and direction by three sides of triangle taken in the same order. The particle will now move with velocity

a)		less than $\vec{v}$
b)		more than $\vec{v}$
c)		$\vec{v}$ only
d)		cannot say

19. Two particles having mass M and m are moving in a circular path having radius R and r. If their time periods are same, then the ratio of angular velocity will be

a)		$\frac{r}{R}$
b)		$\frac{R}{r}$
c)		1
d)		$\sqrt{\frac{R}{r}}$

20. In an elevator moving vertically up with an acceleration 'g' the force exerted on the floor by a passenger of mass M is

a)		Mg
b)		1/2 Mg
c)		zero
d)		2 Mg

21. In a rocket of mass 1000kg, fuel is consumed at a rate of 40 kg/s. The velocity of gases ejected from rocket is 5 $\times$ $10^{4}$ m/s. The thrust on rocket is

a)		2 $\times 10^{3}$ N
b)		5 $\times 10^{4}$ N
c)		2 $\times 10^{6}$ N
d)		2 $\times 10^{8}$ N

22. How does proper inflation of tyres reduce fuel consumption

a)		Normal rection decreases
b)		Normal reaction increases
c)		Sliding contact with road decreases
d)		Sliding contact with road increases

23. A body of weight W is kept on a rough inclined plane having an angle of inclination with the horizontal $θ$ and friction coefficient $μ$ . Force required to pull the body downwards is

a)		W ( $μ$ cos $θ$ + sin $θ$ )
b)		W ( $μ$ cos $θ$ - sin $θ$ )
c)		W (sin $θ$ + $μ$ cos $θ$ )
d)		W ( $μ$ cos $θ$ + 2 sin $θ$ )

24. Two masses A and B each of mass M are fixed together by a massless string. A force act on the mass B as shown below. At the instant the mass has acceleration 'a' . What is the acceleration of mass B

a)		F/M - a
b)		a
c)		-a
d)		F/M

25. lawsofmotionQ8
Two bodies of 5kg and 4kg are tied to a string as shown in above fig. If the table and pulley both are smooth, the acceleration of 5kg mass will be

a)		49 m/ $s^{2}$
b)		5.45 m/ $s^{2}$
c)		19.5 m/ $s^{2}$
d)		2.72 m/ $s^{2}$

26. The electrostatic and gravitational forces are similar because both

a)		are conservative
b)		are central forces
c)		follow inverse square law
d)		All of these

27. A ball weighing 10g hits a hard surface vertically with a speed of 5 m/s and rebounds with same speed. The ball remain in contact with the surface for 0.01 S. The average force exerted by the surface on the ball is

a)		100 N
b)		10 N
c)		1 N
d)		0.1 N

28. A rocket of mass 10,000 kg is to be projected vertically upwards. The gases are exhausted vertically down wards with velocity 1000 m/s w.r.to the rocket. What is minimum rate of burning of fuel so as to just lift the rocket upwards against gravitational attraction

a)		49 kg/sec
b)		147 kg/sec
c)		98 kg/sec
d)		196 kg/sec

29. Two stones of equal mass rest on the pans of an equal arm balance in a lift. Will they remain balanced when the lift accelerates upward

a)		yes
b)		no
c)		The left hand pan will go down
d)		The right hand pan will go down

30. A bullet of mass a and velocity b is fired into a large block of wood of mass c. The final velocity of system is

a)		$\frac{ab}{a + b}$
b)		$\frac{(a + c) b}{c}$
c)		$\frac{ab}{a + c}$
d)		$\frac{(a + c) b}{a}$

31. A block at rest explodes into 3 parts of the same mass. The momentum of the 2 parts are -2p $\hat{i}$ and p $\hat{j}$ . The momentum of the third part will have a magnitude

a)		P
b)		P $\sqrt{3}$
c)		P $\sqrt{5}$
d)		zero

32. A shell is fired from a cannon, it explodes in mild air, its total

a)		Momentum increases
b)		Momentum decreases
c)		K.E increases
d)		K.E decreases

33. A body of mass M is being pulled by a string of mass m with a force P applied at one end.The force exerted by the string on the body will be.

a)		$\frac{Pm}{(M + m)}$
b)		$\frac{Pm}{(M + m)}$
c)		$pm (M + m)$
d)		$\frac{P}{(M - m)}$

34. A particle is projected along the line of greatest slope up a rough plane inclined at an angle of $45^{0}$ with the horizontal.If the coefficient of friction is $\frac{1}{2},$ their retardation is

a)		$\frac{g}{2 \sqrt{2}}$
b)		$\frac{g}{\sqrt{2}}$
c)		$\frac{g}{\sqrt{2}} (1 - \frac{1}{2})$
d)		$\frac{g}{\sqrt{2}} (1 + \frac{1}{2})$

35. Two balls of masses $m_{/}$ and $m_{2}$ are separated from each other by a powdered charge placed between them. The whole system is at rest on the ground.Suddenly the powder charge explodes and the masses are pushed apart. The mass $m_{1}$ travels a distance $s_{1}$ and stops.If the coefficient of friction between the balls and ground are same, the mass $m_{2}$ stops after travelling the distance.

a)		$s_{2} = \frac{m_{1}}{m_{2}} s_{1}$
b)		$s_{2} = \frac{m_{2}}{m_{1}} s_{1}$
c)		$s_{2} = \frac{m_{1}^{2}}{m_{2}^{2}}$
d)		$s_{2} = \frac{m_{2}^{2}}{m_{1}^{2}} s_{1 -}$

36. When a body slides down an inclined plane with coefficient of friction $μ,$ then its acceleration will be

a)		g (sin $θ - μ \cos θ)$
b)		g (sin $θ + μ \cos θ)$
c)		g ( $μ$ sin $θ - \cos θ)$
d)		g ( $μ$ sin $θ + \cos θ)$

37. A block has been placed on an inclined plane.The slope angle $θ$ of the plane is such that the block slides down the plane at a constant speed.The coefficient of kinetic energy is equal to

a)		sin $θ$
b)		cos $θ$
c)		g
d)		tan $θ$

38. A rope ladder with length L carrying a man with a mass m at its end is attached to the basket of a baloon with a massM. The entire system is in equilibrium.If the man begins to climb up the rope ladder with a uniform velocity V relative to the ladder, then the velocity of the baloon is

a)		V
b)		$\frac{mV}{M}$
c)		$\frac{mV}{M + m}$
d)		$\frac{mV}{M - m}$

39. A man weighing 60 kg is standing on a trolley weighing 240 kg.The trolley is resting on frictionless horizontal rails.If the man starts walking on the trolley along the rails at speed 1m/s,then after 4 seconds,his displacement relative to the ground will be

a)		6m
b)		4.8m
c)		3.2m
d)		2.4m

40. A rocket of mass 6000kg is set for vertical firing. If the exhaust speed be 1km/s,how much gas must be ejected to give the rocket an upward acceleration of 20m/ $s^{2} ?$ (Take g=20m/ $s^{2})$

a)		45 kg/s
b)		90 kg/s
c)		120 kg/s
d)		180 kg/s

41. Two skaters weighting in the ratio 4:5 are 9 metre apart, on a smooth frictionless surface.They pull on a rope stretched between them.The ratio of the distance covered by them when they meet each other will be

a)		5:4
b)		4:5
c)		25:16
d)		16:25

42. Five discs each of mass m are placed one above the other.The force on the first from the bottom because of the force on top is

a)		1mg
b)		2mg
c)		3mg
d)		4mg

43. A machine gun is mounted on a 2,000 kg vehicle on a horizontal smooth road(friction negligible).The gun fires 10 bullets per sec with a velocity of 500m/s.If the mass of each bullet be 10g,what is the acceleration produced in the vehicle?

a)		25 cm/ $s^{2}$
b)		25 m/ $s^{2}$
c)		50 cm/ $s^{2}$
d)		50 m/ $s^{2}$

44. A spring is compressed between two toy cars of masses $M_{1}$ and $M_{2} .$ When the cars are released,they move apart.If $x_{1}$ and $x_{2}$ be the displacements of the cars when in contact with the spring,then

a)		$M_{1} x_{1} = M_{2} x_{2}$
b)		$M_{1} x_{2} = M_{2} x_{1}$
c)		$M_{1} x_{1}^{2} = M_{2} x_{2}^{2}$
d)		$M_{1} x_{2}^{2} = M_{2} x_{1}^{2}$

45. A baloon has 8 gram of air.A small hole is pierced into it.The air escapes at a uniform rate of 7cm/s.If the baloon shrinks in 5.6 sec, then the average force acting on the baloon is

a)		$10^{- 4} N$
b)		$10^{- 2} dyne$
c)		56 $dyne$
d)		$10^{- 6} N$

46. The length of an elastic string is x when the tension is 5 N.Its length is y when the tension is 7 N.What will be its length, when the tension is 9N?

a)		2x+y
b)		2x-y
c)		7y-5x
d)		7y+5x

47. A satellite in force-free space sweeps stationary interplanetry dust at a rate (dM/dt)= $α$ v.The acceleration of satellites

a)		${- 2 α v}^{2} / M$
b)		${- α v}^{2} / M$
c)		${- α v}^{2} / 2 M$
d)		${- α v}^{2}$

48. A false balance has equal arms.If an object weighs $w_{1}$ when placed in one pan and $w_{2}$ when placed in the other pan, then the weight w of the object is

a)		$\frac{w_{1} + w_{2}}{2}$
b)		$\frac{w_{1} - w_{2}}{2}$
c)		$\sqrt{w_{1} - w_{2}}$
d)		$\sqrt{w_{1}^{2} - w_{2}^{2}}$

49. Three equal masses A,B and C are pulled with a constant forceF. They are connected to each other with strings.The ratio of the tension between AB and C is
lawsofmotion-q11

a)		1:2
b)		2:1
c)		3:1
d)		1:1

50. An open knife edge of mass M is dropped from a height h on a wooden floor.If the blade penetrates distance 2s into the wood,the average resisitance offered by the wood to the blade is

a)		Mg
b)		Mg $(\frac{1 - h}{s})$
c)		Mg $(1 + \frac{h}{s})$
d)		Mg ${(1 + \frac{h}{s})}^{2}$