1. In the process of pair production, which of the following is a possible product pair? Select one: A. electron-positron B. proton-positron C. electron-proton D. electron-neutron E. proton-neutron 2. Because of their mass, the threshold temperature for electrons is: Select one: A. lower than that of hydrogen. B. lower than that of protons. C. higher than that of hydrogen. D. higher than that of neutrons. E. higher than that of protons.

Non-metals are generally poor conductors of heat and electricity. True or False

________ consists of a community of organisms interacting with their physical environment.

A clean nickel surface (work function 5.1eV), is exposed to light of wavelength 206nm. What is the maximum speed of the photoelectrons emitted from this surface?

What is voltage sensitivity of galvanometer?

A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior.The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm.If the length of the pencil is 14 cm, find the volume of the wood and that of the graphite.[Assume $\mathrm{\pi <!--\; \pi \; -->}=\frac{22}{7}$]

Identify the simple machine used in bicycle.
Lever
Inclined plane
Wheel and axle
Pulley

What is physics in simple words?

What is lateral pressure?

Total Energy of the universe is constant?
Yes, of course
No, it’s conserved but not constant.
Only mechanical energy is conserved.
Can't say

A capacitor has a capacity C and reactance X. If the capacitance and frequency both are doubled, the reactance will become
A. 4X
B.X/2
C. X/4
D.2X

A truck on a straight road starts from rest, accelerating at $2m{s}^{-2}$ , until it reaches a speed of $20m{s}^{-1}$ . Then the truck travels at a constant speed for $20s$ until the brakes are applied causing the truck to decelerate uniformly to stop it in additional $5s$ .
(a) For how much time the truck is in motion?
(b) What is the average speed of the truck for its entire motion?

How was it shown that an atom has empty space?

Why do electrons flow from negative to positive and electric charge flows from positive to negative?

What are the laws of optics?

The volume of air taken in and out of the lungs during normal breathing is called___
tidal volume
residual volume
inspiratory reserve volume
expiratory reserve volume