Problem

The impact wrench consists of a slender 1-kg rod AB which is 580 mm long, and cylindrical...

The impact wrench consists of a slender 1-kg rod AB which is 580 mm long, and cylindrical end weights at A and B that each have a diameter of 20 mm and a mass of 1 kg. This assembly is free to turn about the handle and socket, which are attached to the lug nut on the wheel of a car. If the rod AB is given an angular velocity of 4 rad/s and it strikes the bracket C on the handle without rebounding, determine the angular impulse imparted to the lug nut.

Step-by-Step Solution

Solution 1

Calculate the mass moment of inertia of the section about the axle.

\(=\left[\frac{m\left(L_{A B}\right)^{2}}{12}\right]+2\left[\frac{m R^{2}}{2}+m d^{2}\right]\)

Here, length of the rod \(A B\) is \(L_{A B}\), mass of the rod and the cylinder is \(m\), radius of the cylinder is \(R\) and distance of the center of mass of the cylinder from the centroidal axis is \(d\).

Substitute \(1 \mathrm{~kg}\) for \(m, 600-(2 \times 10) \mathrm{mm}\) for \(L_{A B}, 10 \mathrm{~mm}\) for \(R\) and \(300 \mathrm{~mm}\) for \(d\).

$$ \begin{aligned} I_{a+l_{k}} &=\left[\frac{(1)(600-(2 \times 10))^{2}}{12}\right]+2\left[\frac{(1)\left(\frac{20}{2}\right)^{2}}{2}+(1)(300)^{2}\right] \\ &=28033.33+2(90050) \\ &=208133.33 \mathrm{~kg} \cdot \mathrm{mm}^{2} \times \frac{1 \mathrm{~m}^{2}}{1000000 \mathrm{~mm}^{4}} \\ &=0.208133 \mathrm{~kg} \cdot \mathrm{m}^{2} \end{aligned} $$

Apply the principle of angular impulse and the momentum to the wrench about the handle (or) axle.

Here, the mass moment of inertia of the section about the axle is \(I_{\text {mele }}\) initial angular velocity is \(\omega_{1}\), angular impulse imparted to the lug nut is \(\Sigma \int_{4}^{l_{2}} M_{\text {adt }} d t\) and the angular velocity imparted to the rod \(A B\) is \(\omega_{2}\).

Substitute 0 for \(\omega_{1}, 0.208133 \mathrm{~kg} \cdot \mathrm{m}^{2}\) for \(I_{\text {anle }}\), and \(4 \mathrm{rad} / \mathrm{s}\) for \(\omega_{2}\).

\(I_{a d l} \omega_{1}+\sum \int_{t_{1}}^{l_{2}} M_{a t l e} d t=I_{\sin } \omega_{2}\)

\(0.208133 \times 0+\sum \int_{1}^{t_{2}} M_{a x l e} d t=0.208133 \times 4\)

\(0+\sum \int_{4_{1}}^{t_{2}} M_{a t l} d t=0.8324\)

\(\sum \int_{4}^{t_{2}} M_{a d c} d t=0.8324 \mathrm{~kg} \cdot \mathrm{m}^{2} / \mathrm{s}\)

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