CBSE
A force of acts on O, the origin of the coordinate system. The torque about the point (1, −1) is
C.
A mass of M kg is suspended by a weightless string. The horizontal force that is required to displace it until the string makes an angle of 45° with the initial vertical direction is
A.
The rms value of the electric field of the light coming from the Sun is 720 N/C. The average total energy density of the electromagnetic wave is
3.3 × 10^{−3} J/m^{3}
4.58 × 10^{−6} J/m^{3}
6.37 × 10^{−9} J/m^{3}
81.35 × 10^{−12} J/m^{3}
B.
4.58 × 10^{−6} J/m^{3}
A thin circular ring of mass m and radius R is rotating about its axis with a constant angular velocity ω. Two objects each of mass M are attached gently to the opposite ends of a diameter of the ring. The ring now rotates with an angular velocity ω′
A.
A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. the work done by the force of gravity during the time the particle goes up is
0.5 J
-0.5 J
−1.25 J
1.25 J
C.
−1.25 J
The potential energy of a 1 kg particle free move along the x-axis is given by
The total mechanical energy of the particle 2 J. Then, the maximum speed (in m/s) is
2
B.
A bomb of mass 16 kg at rest explodes into two pieces of masses of 4 kg and 12 kg. The velocity of the 12 kg mass is 4 ms^{−1} . The kinetic energy of the other mass is
144 J
96 J
288 J
192 J
C.
288 J
m_{1}v_{1} = m_{2}v_{2}
Four point masses, each of value m, are placed at the corners of a square ABCD of side A. The moment of inertia through A and parallel to BD is
m
2m
√m
3m
D.
3m
I = 2m (
A particle located at x = 0 at time t = 0, starts moving along the positive x-direction with a velocity ‘v’ that varies as v= α√x . The displacement of the particle varies with time as
t^{3}
t^{2}
t
t^{1/2}
B.
t^{2}