The answer is D=M/V hope it helps!!
Popcorn can be popped by either of the three forms of heat transfer:
Conduction in a pan with hot oil on a stove element.
Convection by an air popper and warm air rising over a heating element... no direct contact with heat source.
Radiation is what occurs in a microwave. Invisible radiant heat activates water molecules in the popcorn.
All the above heat the kernel over 100 Celsius. Water vaporizes/boils (latent heat) and erupts through the kernel.
Mmmm popcorn watch out for the lipids (fat in the oil and butter)
A mass suspended from a spring is oscillating up and down, (as stated but not indicated).
A). At some point during the oscillation the mass has zero velocity but its acceleration is non-zero (can be either positive or negative). <em>Yes. </em> This statement is true at the top and bottom ends of the motion.
B). At some point during the oscillation the mass has zero velocity and zero acceleration. No. If the mass is bouncing, this is never true. It only happens if the mass is hanging motionless on the spring.
C). At some point during the oscillation the mass has non-zero velocity (can be either positive or negative) but has zero acceleration. <em>Yes.</em> This is true as the bouncing mass passes through the "zero point" ... the point where the upward force of the stretched spring is equal to the weight of the mass. At that instant, the vertical forces on the mass are balanced, and the net vertical force is zero ... so there's no acceleration at that instant, because (as Newton informed us), A = F/m .
D). At all points during the oscillation the mass has non-zero velocity and has nonzero acceleration (either can be positive or negative). No. This can only happen if the mass is hanging lifeless from the spring. If it's bouncing, then It has zero velocity at the top and bottom extremes ... where acceleration is maximum ... and maximum velocity at the center of the swing ... where acceleration is zero.
I think you meant what is "Dark matter" if so the answer is Dark matter is a hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe.
