Answer:
a = (v2 - v1) / t
From A to B (8 - 4) m/s / 1 s = 4 m / s^2
From A to D ( 7 - 4) m/s / 5 s = .6 m / s^2
Note these equations hold for "uniform" values
They say nothing about the acceleration at intermediate points - the equation just says that his average speed increased from 4 m/s to 7 m/s during a 5 sec period
There are no good descriptions on that list.
Answer:
Therefore the amplitude of the resultant wave is 
Explanation:
The equation of wave:
y=A sin (kx-ωt)
For wave 1:
y₁=A sin (kx-ωt) =
sin (kx-ωt)
For wave 2:
y₂=A sin (kx-ωt+Φ) =
sin (kx-ωt+Φ)
Where A= amplitude=
The angular frequency 
,
= wave length.
t= time
T= Time period
= phase difference = 
The resultant wave will be
y = y₁ + y₂
=
sin (kx-ωt) +
sin (kx-ωt+Φ)
{sin (kx-ωt) + sin (kx-ωt+Φ)}



Therefore the amplitude of the resultant wave is



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