1. **State the problem:** We have a particle's position function given by $$f(t) = t^2 - \sin(2t)$$ for time $$t$$ in the interval $$0 \leq t \leq 3$$ seconds. We want to analyze the particle's motion by finding:
- Position at $$t=0$$
- Velocity (speed and direction) at $$t=0$$
- Acceleration at $$t=0$$
- Whether the particle is accelerating or decelerating at $$t=0$$
- Average velocity over the interval $$[0,3]$$
2. **Formulas and rules:**
- Position is given by $$f(t)$$.
- Velocity $$v(t)$$ is the first derivative of position: $$v(t) = f'(t)$$.
- Acceleration $$a(t)$$ is the derivative of velocity: $$a(t) = f''(t)$$.
- Average velocity over $$[a,b]$$ is $$\frac{f(b)-f(a)}{b-a}$$.
- Acceleration and velocity signs determine acceleration/deceleration: if they have the same sign, the particle accelerates; if opposite, it decelerates.
3. **Calculate position at $$t=0$$:**
$$f(0) = 0^2 - \sin(0) = 0 - 0 = 0$$
4. **Find velocity function $$v(t)$$:**
$$f(t) = t^2 - \sin(2t)$$
Derivative:
$$v(t) = \frac{d}{dt}(t^2) - \frac{d}{dt}(\sin(2t)) = 2t - 2\cos(2t)$$
5. **Evaluate velocity at $$t=0$$:**
$$v(0) = 2\cdot0 - 2\cos(0) = 0 - 2\cdot1 = -2$$
Velocity is $$-2$$, meaning the particle moves in the negative direction at $$t=0$$.
6. **Find acceleration function $$a(t)$$:**
$$a(t) = \frac{d}{dt}v(t) = \frac{d}{dt}(2t - 2\cos(2t)) = 2 - 2\cdot(-2\sin(2t)) = 2 + 4\sin(2t)$$
7. **Evaluate acceleration at $$t=0$$:**
$$a(0) = 2 + 4\sin(0) = 2 + 0 = 2$$
Acceleration is $$2$$, positive.
8. **Determine acceleration or deceleration at $$t=0$$:**
Velocity is negative ($$-2$$), acceleration is positive ($$2$$), signs differ, so the particle is decelerating at $$t=0$$.
9. **Calculate average velocity over $$[0,3]$$:**
$$\text{Average velocity} = \frac{f(3) - f(0)}{3 - 0}$$
Calculate $$f(3)$$:
$$f(3) = 3^2 - \sin(6) = 9 - \sin(6)$$
Using $$\sin(6) \approx -0.2794$$ (radians),
$$f(3) \approx 9 - (-0.2794) = 9 + 0.2794 = 9.2794$$
So,
$$\text{Average velocity} = \frac{9.2794 - 0}{3} = 3.0931$$
**Final answers:**
- Position at $$t=0$$: $$0$$
- Velocity at $$t=0$$: $$-2$$ (moving backward)
- Acceleration at $$t=0$$: $$2$$ (positive)
- Particle is decelerating at $$t=0$$
- Average velocity over $$[0,3]$$: approximately $$3.093$$
Particle Motion
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