If man were standing unsymmetrically between parallel cliffs, claps his hands and starts hearing a series of echoes at intervals of 1 s. If speed of sound in air is 340 ms', the distance between two cliffs would be
340 m
510 m
170 m
680 m
Half life of a radioactive material is 5 years, then the percentage of it remained after 25 years will be
3.125%
6.25%
1.25%
25%
A.
3.125%
t = 25 years
T1/2 = 5 years
Number of half lives
n =
=
n = 5
Percentage of radio active material remained after 25 year is
= × 100
= × 100
= 3.125 %
The position of a particle moving in the x-y plane at any time t is given by; x = ( 3t3 6t ) meters; y = ( t2 - 2t) meters. Select the correct statement.
acceleration is zero at t = 0
velocity is zero at t = 0
velocity is zero at t = 1s
velocity and acceleration of the particle are never zero
Assertion: A horse has to pull a cart harder during the first few steps of his motion.
Reason: The first few steps are always difficult.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Two masses M1 = 5 kg and M2 = 10 kg are connected at the ends of an inextensible string passing over a frictionless pulley as shown. When the masses are released, then the acceleration of the masses will be
g
g/2
g/3
g/4
The displacement time graph of a particle moving along a straight line is drawn below.
The accelerations of the particle during the regions OP, PQ and QR
OP | PQ | QR |
- | 0 | + |
OP | PQ | QR |
+ | 0 | + |
OP | PQ | QR |
+ | 0 | - |
OP | PQ | QR |
- | + | - |