Answer:
7.5 m/s
Explanation:
We can find its velocity when it reaches the buoy by applying one of Newton's equations of motion:

where v = final velocity
u = initial velocity
a = acceleration
s = distance traveled
From the question:
u = 28 m/s
a = -4 
s = 91 m
Therefore:

The velocity of the boat when it reaches the buoy is 7.5 m/s.
The correct answer is D., density. Hope this helps!
Potential difference across the entire cd player is 12 V
Vb - Va = -366.7 V.
Vab = Va - Vb, the potential of a with respect to b, is equal to the work done by the electric force when a unit of charge moves from a to b, it is given by:
Vab = Va - Vb = Wab/q,
So, in order to determinate the potential difference Vb - Va we have to multiply by -1 both side of the equation above:
- (Va - Vb) = - (Wab/q)
Resulting
Vb - Va = -(Wab/q)
Given a positive charge q = 6.0μC = 6.0x10⁻⁶C, Wab = 2.2x10⁻³J. Determine Vb - Va.
Vb - Va = - (2.2x10⁻³J/6.0x10⁻⁶C)
Vb - Va = -366.7 J/C = -366.7 V