A projectile is moving in a parabolic path.Is there any point at which acceleration is (a)perpendicular to velocity (b)parallel to velocity? Explain.
chapter - motion in a plane (ncert physics for class 11 - part I)
The path of the projectile is parabolic in nature. Let the projectile be thrown with a velocity V at an angle A to the horizontal. The horizontal component of the velocity of the projectile is V*sin A and it is a constant over the entire path.
The vertical component of the velocity of the projectile is Vx = V*cos A initially and it changes following the equation Vy = V*cos A - g*t. At the highest point of the path the magnitude of Vy is equal to 0. The acceleration acting on the projectile is that due to the gravitational force of attraction and is in the vertically downward direction. It is constant and acts throughout the path of the projectile.
At the highest point of the path, the velocity of the projectile only has a horizontal component and here the acceleration is perpendicular to the velocity. The velocity is never parallel to the acceleration as for that to happen the horizontal component would have to be zero which is never the case.