- Thread starter
- #1

#### karush

##### Well-known member

- Jan 31, 2012

- 3,004

**1**What must your car’s $V_{av}$ be in order to travel $\textbf{235 km}$ in $\textbf{2.75 h}$

\begin{align*}\displaystyle

V_{av}&=235km/2.75h \, km/h \\

&=\color{red}{85.45 \, km/h}

\end{align*}

**2**A particle at $t_1 =–2.0 s$ is at $x_1 = 4.8 cm$ and at $t_2 = 4.5 s$ is at $x_2 = 8.5 cm$.}\\

**i**. What is its average velocity over this time interval?\\

**ii.**Can this be calculated. Why or why not?

\begin{align*}\displaystyle

v_{av}&=\frac{x_2-x_1} {t_2-t_1}\\

&=\frac{8.5-(4.8)}{4.5-(-2.0)}\\

&\approx \color{red}{.57}

\end{align*}

**3**A bird can fly $25 km/h$.

How long does it take to fly $3.5 km?$

\begin{align*}\displaystyle

D&=R \cdot T\\

\therefore \frac{D}{R}&=T \\

\frac{25}{60}=\frac{5}{12}&=\frac{3.5}{min}\\

5 \ min&=3.5(12) \\

T&=.7(12)=\color{red}{8.4 \, min}

\end{align*}

Ok I know these are relatively easy problems but they will get harder fast,

there is no book anwswer this is from a class that is already over.

I am trying to format these problems so that they look like a math text book solution

So suggestions are very welcome.

#2 has a

*negative*time in it but I assumed it could be calculated anyway

$$\tiny\textit{Embry-Riddle Aeronautical University Dept of Physical Sciences, HW $\# 1-3$ PS 103 / Technical Physics I}$$