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| <span><img src="../../img/book.png"></span><span>Savchenko Solutions</span> | | <span><img src="../../img/book.png"></span><span>Savchenko Solutions</span> |
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| <p class="author"> | | <p class="author"> |
| Solutions of Savchenko Problems in Physics <br> | | Solutions of Savchenko Problems in Physics <br> |
| <i><b>knowledge must be free</b></i> | | <i><b>knowledge must be free</b></i> |
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| <h3 id="back-link"><a href="../../#2.1">$\leftarrow$Back</a></h3> | | <h3 id="back-link"><a href="../../#2.1">$\leftarrow$Back</a></h3> |
| | | |
| <h3> Statement </h3> | | <h3> Statement </h3> |
| <p> | | <p> |
| $2.1.29.$ A car with a powerful engine, starting from a place, gains a speed of $72$ $\frac{km}{h}$ in $5$ seconds. Find the coefficient of friction between the wheels and the road. What is the shortest braking distance of a car that has reached this speed? | | $2.1.29.$ A car with a powerful engine, starting from a place, gains a speed of $72$ $\frac{km}{h}$ in $5$ seconds. Find the coefficient of friction between the wheels and the road. What is the shortest braking distance of a car that has reached this speed? |
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| <h3>Solution</h3> | | <h3>Solution</h3> |
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| a<center> | | a<center> |
| <figure> | | <figure> |
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| loading="lazy" width="350" /> | | loading="lazy" width="350" /> |
| <figcaption> | | <figcaption> |
| Forces acting on the car | | Forces acting on the car |
| </figcaption> | | </figcaption> |
| </figure> | | </figure> |
| </center> | | </center> |
| | | |
| <p> | | <p> |
| Finding the deceleration value | | Finding the deceleration value |
| $$ a = -\frac{\Delta v}{\Delta t} = -4 \,\frac{m}{s} $$ | | $$ a = -\frac{\Delta v}{\Delta t} = -4 \,\frac{m}{s} $$ |
| | | |
| $$ \Delta t = \frac{\Delta v}{a} $$ | | $$ \Delta t = \frac{\Delta v}{a} $$ |
| 2. The kinematic equations of motion in this case are represented as follows: | | 2. The kinematic equations of motion in this case are represented as follows: |
| $$ \boxed{x=v_0t-\frac{v \Delta t^2}{2}=\frac{v_0^2}{2a}=50 \,m} $$ | | $$ \boxed{x=v_0t-\frac{v \Delta t^2}{2}=\frac{v_0^2}{2a}=50 \,m} $$ |
| Let's find the coefficient of friction $\mu $: | | Let's find the coefficient of friction $\mu $: |
| $$ ma = \mu mg $$ | | $$ ma = \mu mg $$ |
| | | |
| $$ \boxed{\mu = \frac{a}{g} = 0.4} $$ | | $$ \boxed{\mu = \frac{a}{g} = 0.4} $$ |
| </p> | | </p> |
| </p> | | </p> |
