If doubly ionised lithium atom is hydrogen like with atomic number 3, the wavelength of radiation required to excite the electron in Li⁺⁺ from the first to the third Bohr orbit and the number of […]
Activity of a radioactive sample decreases to (1/3)rd of its original value in 3 days. Then, in 9 days its activity will become
Options
(a) (1/27) of the original value (b) (1/9) of […]
If the rise in height of capillary of two tubes is 6.6 cm and 2.2 cm, then the ratio of the radius is
Options
(a) (2:1) (b) 1:√2 (c) (1:2) (d) (1:3)
Correct […]
Four identical rods are joined to from a square. If the temperature difference across one diagonal is 100° C, then temperature difference across another diagonal will be
Options
(a) 100° C (b) 0° […]
A simple pendulum is suspended from the ceiling of a lift. When the lift is at rest its time period is T. With what acceleration should the lift be accelerated upwards in order to reduce […]
The length of second pendulum is 1 m on earth. If mass and diameter of the planet is double than that of earth, then length becomes
Options
(a) 1 m (b) 2 m […]
Four point masses, each of value m, are placed at the corners of a square ABCD of side l. The moment of inertia of this system about an axis through A and parallel to BD […]
The distance travelled by a particle starting from rest and moving with an acceleration 4/3 ms⁻², in the third second is
Options
(a) 10/3 m (b) 19/3 m (c) 6 m (d) 4 m
An aeroplane is flying horizontally with a velocity of 216 km/h at a height of 1960 m. When it is vertically above a point A on the ground, a bomb is released from it. The […]
The angle between the vectors (i+j) and (j+k) is
Options
(a) 90⁰ (b) 60⁰ (c) 30⁰ (d) 45⁰
Correct Answer:
60⁰
Explanation:
A = i + j, B = j + k
A . […]
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