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(problem reference 3 - 2) a projectile fired from a gun has initial horizontal and vertical components of velocity equal to 30 m/s and 40 m/s, respectively.
what is the speed of the projectile when it is at the highest point in its trajectory?
a. 0 m/s
b. 40 m/s
c. 30 m/s
d. 50 m/s

Explanation:

Step1: Analyze projectile motion

In projectile motion, at the highest - point, the vertical component of velocity is 0. The horizontal component of velocity remains constant throughout the motion (neglecting air - resistance) because there is no acceleration in the horizontal direction ($a_x = 0$).

Step2: Identify horizontal velocity

The initial horizontal component of velocity $v_{0x}=30\ m/s$ and it remains the same at the highest point. The speed $v$ at the highest point is equal to the horizontal component of velocity since the vertical component $v_y = 0$ at that point.

Answer:

C. 30 m/s