This is another old O level applied mathematics problem regarding moments. It reads as follows:
A rod $PQ$ is $5 ft.$ long. When a $1 lb.$ mass is hung from $P$ and a $3 lb.$ mas is hung from $Q$, the rod balances at a point $42 in.$ from $P$. When the masses are interchanged, the rod balances at a point $22 in.$ from $P$. Calculate the mass of the rod and the distance of its centre of gravity from $P$.
Solution gives:
$mass = 21 lb.$
$dist. from$ $P = 3 ft.$
I am able to get the distance of $3 ft.$ but am getting the mass of the rod to be $2 lb.$ This seems to be a little light but as I can not obtain the answer for mass given as solution, I am wondering if there is a typo in the book.
If anyone can offer any assistance I would be very grateful.
Not very good at computer code so hope this attachment helps.
Many thanks for any help or advice once again.
Yes, it's a misprint. I did the calculations (independently of your illegible working!), and I got a mass of 2 lb.