Answer:
A line crossing the x-axis in a velocity-time graph means that the moving object has changed its direction.
Explanation:
Velocity-Time graph:
A velocity-time graph is a two dimensional graph with velocity at its y-axis and time at its x-axis. At any point, value of y represents the velocity and value of x represents the time. The slope of the graph gives us the acceleration or deceleration of the moving object.
In a velocity-time graph:
- A straight line represents constant velocity.
- A diagonal line means that the velocity of a body is changing.
*Referring to the figure attached with the answer*
The velocity of the moving object increases at a constant rate for the first 10 minutes. Then the velocity is 60 m/min for the next 5 minutes. After that the velocity is decreasing. Till 30th minute when the velocity is at 0 m/min.
What happens here?
Velocity is a vector quantity. It has some direction. In a velocity-time graph, we are only concerned with two directions of velocity:
- Forward direction
- Backward direction
So, the object stops at 30th minute and starts moving in the reverse direction after that with an increasing velocity. The point where the line cuts the x-axis is basically the point where the object starts moving in the reverse direction.
