Velocity of swimmer across river = 1.30 m/s
Distance arrived downstream = 48 m
Width of river = 64 m
Time taken to cross river = 
= 
Speed of river current = 
= 
So, the river is flowing at a speed 0.975 m/s.
Acceleration is equal to the change in velocity per unit time. In this case, velocity has changed from 17.7 m/s to 14.1 m/s, which is a decrease of 3.6 m/s. This takes place in 12 seconds, so the average acceleration is 3.6 m/s / 12s = 0.3 m/s^2. The direction of this acceleration is south, since the car's northbound speed is decreasing.
Remember that sound intensity decreases in inverse proportion to the distance squared. So, to solve this we are going to use the inverse square formula:
where
is the intensity at distance 2
is the intensity at distance 1
is distance 2
is distance 1
We can infer for our problem that
,
, and
. Lets replace those values in our formula to find
:
dB
We can conclude that the intensity of the sound when is <span>3 m from the source is
30 dB.</span>
Jeremy’s son has more mass, so it would take more forever to reach the same height as his daughter
