Chapter 7, Problem 2P

To determine

The skier’s velocity change.

Answer to Problem 2P

Change of velocity will be y $-7.69\text{ m/s}$ .

Explanation of Solution

Given:

Mass of the skier is m = 65 kg, constant frictional force on the skier is F = 25 N and this force is acted upon the skier in a duration of 1 $\Delta t=20\sec$ .

Formula used:

Since there is a frictional force on the skier, the skier will decelerate. If a be the deceleration of the skier then, 3 $a=-\frac{F}{m}$ . Here, take negative sign, because force is opposite to the motion of the skier. This deceleration results decrease its velocity.

Calculation:

If $\Delta v$ be the change of velocity in the time interval $\Delta t$ =20 sec. Then,

  $a=-\frac{F}{m}=\frac{\Delta v}{\Delta t}$

Substituting the values in the above equation,

  $-\frac{25}{65}=\frac{\Delta v}{20}$

So, change in velocity

  $\begin{array}{c}\Delta v=\frac{-25\times 20}{65} \text{m/s}\\ =-7.69\text{ m/s}\end{array}$

Here negative sign indicates that final velocity decreases, compared to initial velocity.

Conclusion:

Therefore, change in velocity is $\Delta v=-7.69\text{ m/s}$