As our story begins, the sled ... whose mass is 8 kg ... is sliding along the ice at a speed of 4 m/s.
The sled's kinetic energy is (1/2 m v²) = (4 kg · 16 m²/s²) = 64 J .
After what seems like only the blink of an eye, the sled is no longer sliding. It is stationary. Motionless. At Rest. Just sitting there !
Its speed has been reduced to zero and ... because kinetic energy is the energy of motion ... the sled's kinetic energy is now also zero. Sixty-four Joules of energy have disappeared !
How can this be ? ! ? We know that energy is conserved. It can never just appear out of nothing, and it can never just disappear into nothing. If energy suddenly appears, it had to come from somewhere, and if energy suddenly disappears, it had to go somewhere. So where did our 64 Joules of kinetic energy go ?
It went into the ice, THAT's where ! We can say that the sled did 64J of work, and melted a thin slick layer of water on the surface of the ice. OR we can say that friction did NEGATIVE 64J of work on the sled, to cancel the 64J that it had originally, sap its kinetic energy, and bring it to rest.
I think <em>choice-B</em> was supposed to say "<em>B. -64J</em>", but somebody typed it sloppily and neglected to proofread it before posting.
If a capacitor's dielectric constant is vacuum its dielectric constant is k will be equal to 1.
<u>Explanation:</u>
Relative permittivity of a dielectric substance is referred to as its dielectric constant. Relative permittivity/dielectric constant k is a dimensionless quantity that is the ratio of absolute permittivity and vacuum permittivity.
It is given by the expression
k=k=ε /ε0
where ε denotes absolute permittivity and ε0 denotes permittivity of vacuuum.
Absolute permittivity ε of vacuum= ε0
therefore k= ε0/ ε0=1
dielectric constant of vacuum is 1 .
Your answer would be B love!
Answer:
Lunar eclipse
Explanation:
Lunar eclipse occurs when Earth comes in between sun and Moon. The moon is either partially or fully blocked and the moon sighting appears to be black from earth since the light rays coming from sun are blocked by Earth. Lunar eclipse occurs only at full moon. The moon is aligned with the position of earth and sun so that they all form a straight line.
