Saturday, 23 March 2013

WBJEE 2013 online last minutes practice set 1 physics

1. A bard flies for 4 s with a velocity of |t-2| m/s in a straight line, where t=time in seconds. It covers a distance of
a)2 meters
b) 3 meters
c)4 meters
d)5 meters
2. A projectile is moving at 60 m/s at its highest point, where it break into equal parts due to an internal explosion. One part moves vertically up at 50 m/s with respect to the ground. The other part will move at
a)130 m/s
b)120 m/s
c)110 m/s
d)100 m/s
3. A ball falls vertically onto a floor, with momentum p, and then bounces repeatedly. The coefficient of resititution is e. The total momentum imparted by the ball to the floor is
c) p(e+1)/e
d) p/(1-e)
4. A block of mass M is attached to the lower end of a vertical rope of mass m. An upward force P acts on the upper end of the rope. The system is free to move. The force exerted by the rope on the block is PM/(M+m)
a)oly if the rope is uniform
b)only if P > (M+m)g
c)in gravity free space only
d)in all cases
5. A strip of wood of length l is placed on a smooth horizontal surface. An insect starts from one end of the strip, walks with constant velocity and reaches the other end in time t1. It the flies off vertically. The strip moves a further distance l in time t2. Which is true
d)Either a or b depending on the masses of the insect and the strip
6. A man of mass m stands on a frame of mass M. He pulls on a light rope, which passes over a pully. The other end of the rope is attached to the frame. For the system to be in equilibrium, what force must the man exert on the rope
7. A car starts from rest and moves on a surface in which the coefficient of friction between the road and the tyres increases linerarly with distance (x). The car moves with the maximum possible acceleration. The kinetic energy (E) of the car will depend on x as
a)E ∞ 1/x2
b)E ∞ x
c)E ∞ x2
d)E ∞ 1/x
8. A proton mass m collapsed (elastic collision) with an alfa partical mass 4m with velocity 106 m/s. What will be the velocity of the alfa particale
a)4 x 105 m/s
b)4 x 104 m/s
c)4 x 103 m/s
d)4 x 102 m/s
9. A proton mass m collapsed (elastic collision) with an alfa particle mass 4m with velocity 106 m/s. What parsentage of kinetic energy will be transferred to the alfa particle
a)50 %
10. A man who can swim at a speed v relative to the water wants to cross a river of width d, flowing with a speed u. The point opposite him across the river is P
a)The minimum time in which he can cross the river is d/v
b)He can reach the point P in time d/v
c)He can reach the point P in time d/√(v2-u2)
d) All of these
11.In a elastic collision between spheres A and B of equal mass but unequal radii, A moves along the x-axis and B is stationary before impact. Which of the following is possible after impact
a)A comes to rest
b)The velocity of B relative to A remains the same in magnitude but reverses in direction
c)A and B move with equal speeds, making angle of 45° each with the x-axis.
d)All of these possible
12. A monkey of mass m kg slids down a light rope attached to a fixed spring balance, with an acceleration a. The reading of the spring balance is W kg. (g= acceleration due to gravity)
a)The force of friction exerted by the rope on the monkey is m(g-a) N.
c)The tension in the rope is Wg N
d)All of these
13. A ball of mass m attached to the lower end of a light vertical spring of force constant k. The upper end of the spring is fixed. The ball is released from rest with the spring at its normal (unstreched) length, and comes to rest again after descending through a distance x.
b)The ball will have no acceleration at the position where it has descended through x/2
c)The ball will have an upward acceleration equal to g at its lowermost position
d)All of these
14. A uniform heavy chain is placed on a table with a part of it hanging over the edge. It just begins to slide when this part is one-third of its length. The coefficient of friction between the table and the chain is
15. A cannon shell lands 2 km away from the cannon. A second shell, fired identically, breaks into two equal parts at the highest point. One part falls vertically. How far from the cannon will the other land
a)2 km
b)3 km
c)4 km
d)5 km
16. For a system to be equilibrium, the torques acting on it must balance. This is true only if the torques are taken about
a)the center of mass of the system
b)the center of the system
c)any point on the system
d) Any point on the system or out side it
17. Two identical rods are joined to form an 'X'. The smaller angle between the rods is θ. The moment of inertia of the system about an axis passing through the point of intersection of the rods and perpendicular to their plane
a)independent of θ
b)∞ θ
c)∞ cos2θ
d)∞ sin2θ
18. A body of mass m is moving with a constant velocity akong a line parallel to the x-axis, away from the origin. Its angular momentum with respect to the origin
a)is zero
b)goes on increasing
c)goes on decreasing
d)remains constant
19. A ring of radius r and mass unit length m rotates with an angular velocity ω in free space. The tension in the ring is
a)m r ω2
b)½ m r2ω2
c)m r2ω2
20. P is the center of mass of four point masses A,B,C and D which are coplanar but not collinear.
a)P may or may not coincide with one of the point masses
b)P must lie within the quadrilateral ABCD
c)P must lie within or on the edge of at least one of the triangles formed by taking A,B,C and D three at a time
d)a and c
Set 1 | Set 2 | Set 3 | Set 4 | Set 5 | Set 6

References: 1. A guide to physics problem--C.R.D.G. 2. Physics mcq - D Mukherjee
© Engg. Suman Biswas B.Tech (I.T)

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