Question

As a projectile moves through its parabolic trajectory, which of the following quantities does NOT remain constant?

A) Horizontal velocity

B) Vertical velocity

C) Vertical acceleration

D) Horizontal acceleration

Answer 1

Vertical velocity does not remain constant for a projectile in motion since it is influenced by gravity, unlike horizontal velocity and vertical acceleration which remain constant (horizontal acceleration is zero). The graph of vertical acceleration versus time for a launched ball shows a constant negative value.

Step-by-step explanation:

As a projectile moves through its parabolic trajectory, the quantity that does NOT remain constant is B) Vertical velocity. The vertical velocity changes due to the influence of gravity. The horizontal velocity (A) remains constant (assuming no air resistance), and the vertical acceleration (C) due to gravity also remains constant with a negative value as it is directed downwards towards the ground, which would mean that the horizontal acceleration (D) is zero.

In an experiment where a ball is launched with an initial horizontal velocity at an elevation, the graph of the ball's vertical acceleration versus time would show a negative value that does not change with time, indicating a constant downward acceleration. Thus, the correct answer is a. A negative value that does not change with time. Objects in projectile motion experience this constant vertical acceleration due to gravity, irrespective of their initial horizontal velocities.

Answer 2

B) Vertical velocity

Step-by-step explanation:

To address the question regarding the constancy of specific quantities in a projectile's parabolic trajectory, it's important to understand the fundamental principles of projectile motion. Projectile motion involves two independent components: horizontal and vertical motions. Here is a breakdown of each option:

• A) Horizontal Velocity: This remains constant in projectile motion. The horizontal component of velocity does not change because there is no horizontal acceleration acting on the projectile.

• B) Vertical Velocity: This does not remain constant. The vertical component of the velocity changes due to the influence of gravity. Initially, when a projectile is launched upwards, its vertical velocity decreases until it reaches the peak of its trajectory, where the vertical velocity is zero. Then, as it falls back down, the vertical velocity increases in the opposite direction.

• C) Vertical Acceleration: This remains constant and is equal to the acceleration due to gravity (approximately 9.8 m/s² downwards). The vertical acceleration due to gravity is a constant value, influencing the change in vertical velocity.

• D) Horizontal Acceleration: This is essentially zero in ideal projectile motion. Since horizontal acceleration is absent, the horizontal velocity remains constant.

Therefore, the quantity that does NOT remain constant in a projectile's parabolic trajectory is the Vertical Velocity, option (B).

Note: The above explanation assumes there is no air friction.