The star is the main sequence
Answer:
D
Explanation:
reactants have higher potential energy and energy is absorbed
The heat pump is a thermal machine that takes heat from a cold space and transfers it to a hotter one thanks to a work provided from the outside, that is, it does exactly the same as the refrigerating machine, the only thing that changes is the objective (In the refrigerating machine the objective is to cool and keep the cold space cold. The heat pump, however, aims to provide heat and keep the hot space warm)
Therefore the correct answer is A. <em>A heat pump uses work to transfer energy by heat from a colder environment to a warmer environment.</em>
Answer: His acceleration is -18.66m/s^2
Explanation:
Ok, the initial speed is 2.8m/s. (we can define the initial direction as the positive direction).
And he wants to stop, so he must accelerate in the opposite direction as the initial movement, then we would have:
a(t) = -A.
So we have a constant, and negative acceleration.
Now, if we want to find the velocity we must integrate over time, and we will get:
v(t) = -A*t + V0
where V0 is the initial velocity, we know that it is 2.8m/s, and t is the time in seconds.
Then the velocity is:
v(t) = -A*t + 2.8m/s.
Now we know that John is brought to rest in 0.15 seconds after he starts slowing down, this means that at t = 0.15 seconds, his velocity is equal to zero.
v(0.15s) = 0m/s = -A*0.15s + 2.8m/s
2.8m/s = A*0.15s
2.8m/s/0.15s = 18.66m/s^2 = A.
So his acceleration is -A, then we have that:
His acceleration is -18.66m/s^2
