The half-life of a radioactive substance is

• A. its average life time
• B. one-half the value of its decay constant.
• C. the length of time needed by the substance to decay completely
• D. the length of time during which the activity of the substance reduces by 50%.

In an electrolysis experiment, the ammeter records a steady current of 1 A. The mass of copper deposited in 30 minutes is 0.66 g. Calculate the error in the ammeter reading. [ Electrochemical equivalent of copper = 0.00033 g C\(^{-1}\)]

A Motor Tyre is inflated to pressure of 2.0 x 10⁵Nm^-2 when the temperature of air is 27^oC. What will be the pressure in it at 87^oC assuming that the volume of the Tyre does not change?

• A. 2.6 x 10⁵Nm^-2
• B. 2.4 x 10⁵Nm^-2
• C. 2.2 x 10⁵Nm^-2
• D. 1.3 x 10⁵Nm^-2

If a pump is capable of lifting 5000kg of water through a vertical height of 60m in 15 min, the power of the pump is

• A. 2.2.5 x 10⁵js^-1
• B. 2.5 x 10⁴js^-1
• C. 3.3 x 10³js^-1
• D. 3.3 x 10²js^-1

The effect of closing the key K in the circuit shown in the figure above would be to?

• A. increase the current by 0.4A
• B. reduce the current by 0.4A
• C. increase the current by 0.6A
• D. reduce the current by 0.6A

The diagram below represents the displacement-time graph of the motion of an object thrown upwards. The velocity of the object at the point P is

• A. maximum
• B. uniform
• C. zero
• D. terminal

The horizontal floor of a water reservoir appears to be 1.0m deep when viewed vertically from above. If the refractive index of water is 1.35, calculate the real depth of the reservoir

• A. 2.35m
• B. 1.35m
• C. 1.00m
• D. 0.35m

what part of the camera corresponds to the iris of the eye?

• A. shutter
• B. film
• C. lens
• D. diaphram

A car accelerates uniformly from rest at 3ms^-2. its velocity after traveling a distance of 24m is

• A. 12ms^-1
• B. 144ms^-1
• C. 72ms^-1
• D. 36ms^-1

The diagram below illustrates a beam of parallel rays from a distant object O, incident on one side of the total reflecting prism. Which diagram does not represent the correct path of the beam when it emerges from the prism?

• A. W
• B. X
• C. Y
• D. Z