Observe: Click Reset. Turn on Show velocity vector and Show velocity components. Set vinitial to 50 m/s and set θ to 45.0 degrees. Click Play. Focus on the blue and red arrows that represent the vertical and horizontal components of the golf ball’s velocity. As the ball flies through the air, what do you notice about the blue (vertical) arrow?

v_y = v_{oy} - g t

where the upward direction is positive, so the arrow represents this speed (blue) must decrease, reach zero and grow in a negative direction as time progresses

Explanation:

In this exercise you are asked to observe the change in velocity in a projectile launch.

If we assume that the friction force is small, the velocity in the x-axis must be constant

         vₓ = v₀ₓ

Therefore, the arrow (red) that represents this movement must not change in magnitude.

In the direction of the y axis, the acceleration of gravity is acting, so the magnitude of the velocity in this axis changes

         v_y = v_{oy} - g t

where the upward direction is positive, so the arrow represents this speed (blue) must decrease, reach zero and grow in a negative direction as time progresses

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