Q."It is the velocity not the acceleration which decides the direction of motion of a body". Justify this statement with the help of a suitable example.
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Start your 14-day free trial to unlock the full solution →Direction of motion = direction of velocity at that instant; acceleration merely tells us how velocity is changing over time, and can point in a completely different direction from the motion itself.
By definition, velocity is the rate of change of the position vector, so the direction in which a body is instantaneously moving IS the direction of its velocity vector at that instant. Acceleration, by contrast, is the rate of change of velocity -- it tells us whether the velocity is increasing, decreasing, or changing direction, but the body's actual direction of travel at any given moment is set entirely by its velocity, not by its acceleration.
Example -- a ball thrown straight up:
When a ball is thrown vertically upward with some initial speed, gravity provides a constant acceleration g that acts DOWNWARD throughout the entire flight (both while going up and coming down).
- On the way up: the ball's velocity points upward, so the ball moves upward -- even though its acceleration (g, downward) is opposite to this direction the whole time. The downward acceleration is simply slowing the upward velocity down (decelerating it), not making the ball move downward.
- At the highest point: the velocity becomes momentarily zero, but the acceleration is still g, downward (non-zero). …
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