Which of the curves in the graph below best represent the vertical component Vy of the velocity versus the time t for a projectile fired at an angle of 45 above the horizontal??

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1 Answer
Jun 28, 2017

D
After projectile is fired, initial vertical component of velocity decreases under retarding force of gravity, becomes stationary momentarily at the maximum height, then increases in the downward (-ve) direction as the projectile falls freely under gravity.

Explanation:

Vertical component of velocity of projectile is given by the kinematic expression

v=u+at

In our case

v_y(t)=v_(y0)-g t
Acceleration due to gravity g is taken as -ve as it is in a direction opposite to direction of initial vertical velocity v_(y0).

Rearrange and notice that it represents a straight line. Compare it with standard equation.

y=mx+c
v_y(t)=-g t+v_(y0)

Slope of the line is negative. Makes an angle greater than 90^@ with x-axis.