A projectile is shot upwards from the surface of the earth with an initial velocity of 108 meters per second. The position function is $s ( t ) = - 4.9 t ^ { 2 } + v _ { 0 } t + s _ { 0 }$ What is its velocity after 7 seconds?
A) The velocity after 7 seconds is $181.7$ meters per second.
B) The velocity after 7 seconds is $- 142.3$ meters per second.
C) The velocity after 7 seconds is $39.4$ meters per second.
D) The velocity after 7 seconds is $73.7$ meters per second.
E) The velocity after 7 seconds is $- 176.6$ meters per second.

Question

Quizplus · Accepted Answer

The velocity function is the derivative of the position function: $v(t) = -9.8t + v_0$. Substituting $t = 7$ and $v_0 = 108$, we get $v(7) = -9.8(7) + 108 = 39.4$ meters per second.

A Projectile Is Shot Upwards from the Surface of the Earth