1. **State the problem:** Calculate the height $S(t)$ of an object thrown upwards with initial velocity $v_0=28$ m/s from an initial height $h_0=3$ m after $t=2$ seconds, under gravity $g=9.8$ m/s$^2$.
2. **Formula:** The height as a function of time is given by
$$S(t) = -\frac{1}{2} g t^2 + v_0 t + h_0$$
where $-\frac{1}{2} g t^2$ accounts for the downward acceleration due to gravity.
3. **Substitute values:**
$$S(2) = -\frac{1}{2} \times 9.8 \times 2^2 + 28 \times 2 + 3$$
4. **Calculate each term:**
$$-\frac{1}{2} \times 9.8 \times 4 = -\frac{1}{2} \times 39.2 = -19.6$$
5. **Sum all terms:**
$$S(2) = -19.6 + 56 + 3$$
6. **Simplify:**
$$S(2) = (-19.6 + 56) + 3 = 36.4 + 3 = 39.4$$
7. **Final answer:**
The height after 2 seconds is $\boxed{39.4}$ meters.
**Note:** Your original calculation had an error in summing the terms; the correct height is 39.4 m, not 20.3 m.
Height Calculation 5C6Aa6
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