They do the method 3 times to be sure. Because if you do it once, that could mean anything. If you do it twice, it may or may not have the same result. If you do it 3 times and it matches one of the previous answers, then it's likely that it's correct.
It magnifies light received from distant objects.
I believe it is acceleration!
The representation of this problem is shown in Figure 1. So our goal is to find the vector
. From the figure we know that:
From geometry, we know that:
Then using
vector decomposition into components:
Therefore:
So if you want to find out <span>
how far are you from your starting point you need to know the magnitude of the vector
, that is:
</span>
Finally, let's find the <span>
compass direction of a line connecting your starting point to your final position. What we are looking for here is an angle that is shown in Figure 2 which is an angle defined with respect to the positive x-axis. Therefore:
</span>
Acceleration = (change in speed) / (time for the change)
Change in speed = (later speed) - (earlier speed) = (13 - 24) = -11 km/hr
Time for the change = 2 seconds
Acceleration = (-11 km/hr) / (2 sec)
Acceleration = -5.5 km/hr-sec (B)