Physics
Physics
Problem
When a ball is thrown vertically upward, which one of the following correctly describes the sign that should be taken for the acceleration due to gravity in the equations of motion (upward direction taken as positive)? a) Positive b) Zero c) Negative d) Depends on the direction of motion of the ballIntuitive explanation
The key insight is that represents the magnitude of gravitational acceleration, while the sign in your equation captures the direction of the force. Since you've defined upward as positive, gravity—which always pulls downward—must be represented as in your kinematic equations. This consistent sign convention ensures that acceleration, velocity, and displacement all work together correctly throughout the ball's flight, whether it's rising, at the peak, or falling.
Intuitive explanation
The key insight is that represents the magnitude of gravitational acceleration, while the sign in your equation captures the direction of the force. Since you've defined upward as positive, gravity—which always pulls downward—must be represented as in your kinematic equations. This consistent sign convention ensures that acceleration, velocity, and displacement all work together correctly throughout the ball's flight, whether it's rising, at the peak, or falling.