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.
1) 20 min = 1/3 h
2) distance = speed * time = 12 * 1/3 = 4 km
Answer:
one sister, one half-brother, and three cousins.
Explanation:
Kin selection theory also called inclusive fitness theory describes the self-sacrificial behaviour of organism, animal or individual to ensure survival of closely related family at the detriment of the individual's survival in order to preserve genetic fitness or survival and reproductive success of such individual. Therefore saving one sister, one half-brother, and three cousins will preserve the genetic lineage and reproductive success of the genome of interest
Her displacement would be -3 blocks
displacement = final position - initial position
This is most likely True. However, it could be also False. Let me explain.
There are many air pollutants that can be found outdoors and indoors. It does depend on what kind of indoor environment we're talking about. And also what kind of outdoor environment we're talking about. In both cases it depends on the context. If the indoor environment is quite toxic, then of course, there would be less cancer-causing air pollutants for a person outside. And the same is true for the other way around.
