Answer:
20.4m/s²
Explanation:
Given parameters:
Initial velocity = 0m/s
Distance = 53m
Time = 5.2s
Unknown:
Acceleration = ?
Solution:
This is a linear motion and we use the right motion equation;
S = ut +
at²
S is the distance
u is the initial velocity
a is the acceleration
t is the time
Insert the parameters and solve;
53 = (0x 5.2) +
x a x 5.2
53 = 2.6a
a =
= 20.4m/s²
To solve this problem we need to apply the corresponding sound intensity measured from the logarithmic scale. Since in the range of intensities that the human ear can detect without pain there are large differences in the number of figures used on a linear scale, it is usual to use a logarithmic scale. The unit most used in the logarithmic scale is the decibel yes described as

Where,
I = Acoustic intensity in linear scale
= Hearing threshold
The value in decibels is 17dB, then

Using properties of logarithms we have,




Therefore the factor that the intensity of the sound was 
Answer:
D. Sand carried by rivers flows over and weathers the rocks.
Explanation:
The sand in the river is move because of the flow of the river and as the sand moves it grinds on the rocks in the river. This starts a process know as abrasion, in other words it means that it wheathers(grinds) against the rocks.