Question

Your friend says you can't use the equation Ax = v0At + a (At)2 to find the horizontal
displacement of a horizontal projectile with a constant horizontal velocity because you don't know the
acceleration in the horizontal direction. Is your friend correct? Why or why not?
answers:
My friend is incorrect. The acceleration is always -9.8 m/s2.

My friend is incorrect. The horizontal acceleration is the same as horizontal velocity.

My friend is incorrect. If the velocity is constant, then the horizontal acceleration is zero.

My friend is correct. A different equation must be used to find A.x.

Answer 1

Your friend is incorrect. The correct interpretation is:

**My friend is incorrect. If the velocity is constant, then the horizontal acceleration is zero.**

In the case of a horizontal projectile, the horizontal motion occurs with a constant velocity because there is no horizontal acceleration acting on the projectile. This means that you can use the simple equation for constant velocity:

\[ x = v_{0x} \cdot t \]

where \( v_{0x} \) is the initial horizontal velocity and \( t \) is the time of flight. Since the horizontal acceleration is zero, you do not need to consider any acceleration terms in your calculations for horizontal displacement. The vertical motion, however, is influenced by the acceleration due to gravity, which is why your friend might be confused. However, this does not affect the horizontal displacement calculation.