Question

A pesky rabbit has been feeding on Mrs. Cromwell’s prized flowers. In order to put an end to this she devised the simple trap below to catch the rabbit. The crate weighs 13lb and is supported by stick BC. Find the minimum diameter of stick BC if the normal stress in it is limited to 100 psi.

Answer 1

Answer:

The minimum diameter of the stick to bear the normal stress as 100 psi is 0.1785 in.

Explanation:

Taking moment along point A

$\sum M_A=0\\F_{BC} sin 60 \times 48 -13 \times 8=0\\F_{BC}=2.502 lb_f$

Also normal stress is given as 100 psi

Now

                      $\sigma=\frac{F}{A}\\100=\frac{2.502}{\pi \frac{d^2}{4}}\\d^2 =\frac{4 \times 2.502}{100 \pi }\\d^2=0.031856\\d=\sqrt{0.031856}\\d=0.1785 inch$

The minimum diameter of the stick to bear the normal stress as 100 psi is 0.1785 in.