Multiple Choice QuestionsAn explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are 1 kg first part moving with a velocity of 12 ms-1 and 2 kg second part moving with a velocity of 8 ms-1.If the third part flies off with a velocity of 4 ms-,its mass would be
5 kg
7 kg
17 kg
17 kg
A.
5 kg
apply the law of conservation of linear momentum.
momentum of first part = 1 x 12 = 12 kg ms-1
Momentum of the second part = 2 x 8 = 16 kg ms-1 '
Resultant monmentum
= [(12)2 +(16)2]1/2 = 20 kg ms-1
The third part should also have the same momentum.
If the dimensions of a physical quantity are given by Ma Lb Tc, the physical quantity will be
pressure if a = 1, b = -1, c= 2
velocity if a = 1, b = 1, c = -2
acceleration if a = 1, b = 1, c =-2
acceleration if a = 1, b = 1, c =-2
Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle
depends on v and not on R
depends on R and not on v
is independent of both v and R
is independent of both v and R
A body mass 1 kg is thrown upwards with velocity 20 ms-1. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction? (g = 10 ms-2)
20 J
30 J
40 J
40 J
The mass of a lift is 2000 kg. When the tension in the supporting cable is 28000 N, then its acceleration is
30 ms-2 downward
4 ms-2 upwards
4 ms-2 downwards
4 ms-2 downwards
A particle starts its motion from rest under the action of a constant force. If the distance covered in first 10 s is s1 and that covered in the first 20 s is s2, then
s2 = 2s1
s2 = 3s1
s2 = 4 s1
s2 = 4 s1
A thin circular ring of mass M and radius R is rotating in a horizontal plane about an axis vertical to its plane with a constant angular velocity ω. If two objects each of mass m be attached gently to the opposite ends of a diameter of the ring. the ring will then rotate with an angular velocity
Two bodies of mass 1 kg have position vectors,
respectively.The centre of mass of this system has a position vector
Four identical thin rods each of mass M and length l , inertial form a square frame. moment of inertia of this frame about an axis through the centre of the square and perpendicular to this plane is
4Ml2/3
2Ml2/3
13Ml2/3
13Ml2/3
The figure shows elliptical orbit of a planet m about the sun S. The shaded are SCD is twice the shaded area SAB. If t1 is the time for the planet to move from C to D and t2 is the time to move from A to B then,
t1 > t2
t1 =4 t2
t1 = 2t2
t1 = 2t2
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