Keeping in mind that the conversion between calories and Joules is
we can write the conversion factor using the kilocalories:
The energy released in our problem is
so we can set a simple proportion to find its equivalent in kcal:
from which we find:
<span>It is important to emphasize that this statement of the 2nd law applies to the spontaneous flow of heat from hot to cold. It is possible, of course, to make a cool object in a warm place cooler - this is what a refrigerator does - but this involves the input of some external energy. As such, the flow of heat is not spontaneous in this .</span>
D. The answer is D because any other scenario is possible. For example, in A, John could very easily put the planets in order. In problem B, he could draw some planets bigger than others. On C, he could color the planets on a different color. He can not hovever, move the planets
I'm pretty sure it's a plane mirror? A plane mirror has a flat (but reflective) surface. It might be what you're looking for.
Answer:
a) -4 N
b) +4 N
Explanation:
Draw a free body diagram for each block.
For the large block, there are 2 forces: 12 N pushing to the right, and F pushing to the left.
For the small block, there is 1 force, F pushing to the right.
There are also weight and normal forces in the vertical direction, but we can ignore those.
Sum of forces on the large block in the x direction:
∑F = ma
12 − F = 4a
Sum of forces on the small block in the x direction:
∑F = ma
F = 2a
2F = 4a
Substitute:
12 − F = 2F
12 = 3F
F = 4
The small block pushes on the large block 4 N to the left (-4 N).
The large block pushes on the small block 4 N to the right (+4 N).