Multiple Choice QuestionsA car of mass m starts from rest and accelerates so that the instantaneous power delivered to the car has a constant magnitude Po. The instantaneous velocity of this car is proportional to
t2Po
t1/2
t-1/2
t-1/2
A body of mass (4m) is lying in x-y plane at rest. It suddenly explodes into three pieces. Two pieces each of mass m move perpendicular to each other with equal speed (v). The total kinetic energy generated due to explosion is,
mv2
2mv2
2mv2
B.
A 200 W sodium street lamp emits yellow light of wavelength 0.6 um. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is
1.5 x 1020
6 x 1018
62 x 1020
62 x 1020
Two cities are 150 km apart. electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 V and the average resistance per km is 8 V and the average resistance per km is 
. The power loss in the wire is,
19.2 W
19.2 kW
19.2 J
12.2 kW
A body of mass m taken from the earth's surface to the height equal to twice the radius (R) of the earth. The change in potential energy of the body will be
mg2R
2/3 mgR
3 mgR
3 mgR
The potential energy of a system increase if work is done
By the system against a conservative force
By the system against a nonconservative
upon the system by a conservative force
upon the system by a conservative force
A ball is thrown vertically downwards from a height of 20m with an initial velocity vo, It collides with the ground, loses 50% of its energy in collision and rebounds to the same height. The initial velocity vo is,
(Take g = 10 ms-2)
14 ms-1
20 ms-1
28 ms-1
28 ms-1
The heart of a man pumps 5 L of blood through the arteries per minute at a pressure of 150 mm of mercury . If the density of mercury be 13.6 x 103 kg/ m3 and g = 10 m/s2, then the power of heart in watt is
1.70
2.35
3.0
3.0
On a frictionless surface, a block of mass M moving at speed v collides elastically with another block of same mass M which is initially at rest. After collision, the first block moves at an angle θ to its initial direction and has a speed v/3/ The second block's speed after the collision is
3/4 v
An engine pumps water through a hosepipe. Water passes through the pipe and leaves it with a velocity of 2 ms-1. The mass per unit length of water in the pipe is 100 kgm-1. What is the power of the engine?
400 W
200 W
100 W
100 W
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