Bullet Maximum Height
1. **Problem Statement:**
A bullet is shot upwards with an initial velocity of 200 ft/sec from a point 30 ft above the ground. Its height at time $t$ seconds is given by the quadratic function:
$$h(t) = -25 t^2 + 200 t + 30$$
We need to find:
(i) The maximum height the bullet reaches.
(ii) The time it takes to reach this maximum height.
2. **Formula and Explanation:**
The height function $h(t)$ is a quadratic function of the form:
$$h(t) = at^2 + bt + c$$
where $a = -25$, $b = 200$, and $c = 30$.
Since $a < 0$, the parabola opens downward, so the vertex represents the maximum point.
The time $t$ at which the maximum height occurs is given by the vertex formula:
$$t = -\frac{b}{2a}$$
3. **Calculate the time to reach maximum height:**
$$t = -\frac{200}{2 \times (-25)} = -\frac{200}{-50} = 4$$ seconds.
4. **Calculate the maximum height:**
Substitute $t=4$ into $h(t)$:
$$h(4) = -25(4)^2 + 200(4) + 30 = -25(16) + 800 + 30 = -400 + 800 + 30 = 430$$ feet.
5. **Summary:**
- The bullet reaches its highest point at $t=4$ seconds.
- The maximum height is $430$ feet.
This means the bullet will rise to 430 feet above the ground after 4 seconds before starting to fall back down.