During an interval of time, a tennis ball is moved so that the angle between the velocity and the acceleration of the ball is kept at a constant 120ยบ. Which statement is true about the tennis ball during this interval of time?
Choose one answer.a. Its speed decreases and it is changing its direction of travel.
b. Its speed remains constant, but it is changing its direction of travel.
c. Its speed decreases and it is not changing its direction of travel.
d. Its speed increases and it is changing its direction of travel.
e. Its speed remains constant and it is not changing its direction of travel
In my mind the ball is travelling with a negative velocity, south, all in the y component. At the time it is being accelerated at 120 degrees, thus it is slowing down in the negative Y direction. "Its speed decreases and it is not changing direction of travel." That is, it will eventually change its direction of travel, but just because it is accelerating in the opposite direction of the current vector does not mean that it has changed direction; yet. The answer is given as "a." But couldn't "a." or "c." be true?
Best Answer
I think this is the core of your confusion. The object is not accelerating in the opposite direction of the current velocity. Try drawing a diagram of the two vectors and you'll see what I'm talking about.