Chapter 9, Problem 7STP

To determine

To Choose: The correct option.

Answer to Problem 7STP

Option A. $0.2\text{kg}$

Explanation of Solution

Given:

Impulse on the object, $\text{Impulse = 0}\text{.8 kg}\cdot \text{m/s}$

Final speed of the rock, $v_f=4.0\text{m/s}$

Formula used:

Momentum of an object of mass m and moving with velocity v is given by,

  $p=mv$

And, impulse on an object is given by the change in momentum of the object,

  $\text{Impulse = }{p}_f-p_i$

Calculation:

Since initially the rock was on ground, thus its initial velocity will be zero,

  $v_i=0\text{m/s}$

Using the given values in above mentioned formulas, the mass of the rock will be,

  $\begin{array}{c}\text{Impulse = }{p}_f-p_i\\ 0.8=m\left(v_f-v_i\right)\\ =m\left(4.0-0\right)\\ m=0.2\text{kg}\end{array}$

Conclusion:

Thus, the mass of the rock is $0.2\text{kg}$ .