Answer:
a. at either A or B
Explanation:
Kinetic energy may be defined as the energy of the system or an object which is due to its velocity of the object it possess.
In the context, an object having mass is attached to spring which is vertical and the object moves up and down due to spring effect between points A and B. Now these points A and B are the extreme points after which the object bounces back.
At point A and B, the velocity of the object becomes zero and hence the kinetic energy of a body varies directly proportional to its velocity.
i.e. Kinetic energy 
The Law of reflection would still hold even off a curved surface. Since the angles are measured from the normal, which is perpendicular to the surface, curved surfaces don't matter. This is basis of curved mirrors such as concave and convex
The change in electric potential energy is given by:
ΔU = ΔVq
ΔU = change in PE, ΔV = potential difference, q = charge
Given values:
ΔV = 50V - 20V = 30V, q = 0.14C
Plug in and solve for ΔU:
ΔU = 30(0.14)
ΔU = 4.2J
The height of the bullet when the velocity is zero is 256 ft.
<h3>Height of the bullet when the velocity is zero </h3>
The height of the bullet when the velocity is zero is determined by taking derivative of the function as shown below;
The height of the bullet at this time is calculated as follows;
Learn more about height of projectiles here: brainly.com/question/10008919
