During the first phase of acceleration we have:
v o = 4 m/s; t = 8 s; v = 13 m/s, a = ?
v = v o + a * t
13 m/s = 4 m / s + a * 8 s
a * 8 s = 9 m/s
a = 9 m/s : 8 s
a = 1.125 m/s²
The final speed:
v = ?; v o = 13 m/s; a = 1.125 m/s² ; t = 16 s
v = v o + a * t
v = 13 m/s + 1.125 m/s² * 16 s
v = 13 m/s + 18 m/s = 31 m/s
Answer:

Explanation:
When heat energy is supplied to an object, the temperature of the object increases according to the equation:

where
Q is the heat supplied
C is the heat capacity of the object
is the change in temperature
In this problem we have:
is the energy supplied
is the change in temperature of the object
Therefore, the heat capacity of the object is:

When light passes from a faster medium into a slower medium, light will be refracted toward a line drawn perpendicular to the point of refraction. <em>(B)</em>