Question

When a projectile is fired at an angle theta above horizontal with velocity v , then the magnitude of its vertical component of velocity :- (1).remains same (2).goes on increasing (3).first increases and then decreases (4).first decreases and then increases

Answer 1

Answer:

4) first decreases and then increases

Answer 2

Answer:

The vertical velocity first decreases, reaches zero at maximum height and then increases.

Explanation:

Given a projectile is fired at an angle θ with horizontal axis with velocity v.

• The projectile moves along a curved path under under the force of gravity, and the motion is called projectile motion.
• The motion of projectile is a two dimensional motion. Therefore, the velocity $v$ can be resolved into two components $vcos\theta$ along x-axis and $vsin\theta$ along y-axis.
• The horizontal distance is covered by the velocity $vcos\theta$ and the vertical distance by the vertical velocity $vsin\theta$.
• Vertical velocity gets affected by force of gravity, whereas the horizontal velocity remains constant.
• When the projectile is moving upwards, acceleration due to gravity acts downwards. Therefore, with  increase in the height, the vertical velocity decreases and becomes zero at maximum height.
• From the maximum height, it fall down freely with increasing vertical velocity.

So the vertical velocity first decreases while going up, reaches zero at maximum height and then increases while coming down

Hence, the correct option is 4.