Question

The slope of a velocity-time graph for the free fall of a body under gravity, starting from rest is (Take $g=10m{s}^{-2}$.)

• A. $10m/s^2$.
• B. $-10m/s^2$.
• C. $0m/s^2$.
• D. $1m/s^2$.

Answer 1

The correct option is B $-10m/s^2$.

The line on the velocity-time graph for the free fall of a body under gravity is a straight line. A free-falling object is undergoing an acceleration (g = $10m{s}^{-2}$, downward). A further look at the velocity-time graph reveals that the object starts with a zero velocity (as read from the graph) and finishes with a large, negative velocity; that is, the object is moving in the negative direction and speeding up. An object that is moving in the negative direction and speeding up is said to have a negative acceleration. Since the slope of any velocity versus time graph is the acceleration of the object, the constant, negative slope indicates a constant, negative acceleration.
Below is the diagrammatic representation.