Tennis Tension

It’s a week since Wimbledon finished and I have just got back from playing tennis (we went last week, immediately after Murray’s victory to find that both of our village tennis courts were in use when we got there; this is the first time this has ever happened!).  I like to think this means we weren’t just caught up in Murray-mania.

I hadn’t noticed before that my racquet includes information about string tension, printed in the V-shape where the head meets the handle.

A couple of things are a little strange.  Have a look.

First of all, the tension, which is a force, is given in kg (a unit of mass).

Secondly, the two ranges don’t appear to match up.  The KGS range is 16% of the lower figure.  If you increase the lower end of the LBS by 16% you get to 63.8 lb

So let’s look at the conversion factor for pounds and kg.  1kg is equivalent to 2.205lb (to 4sf).

25kg is equivalent to 55.125lb

29kg is equivalent to 63.945lb

Hmm - it looks as if the imperial set of figures is wrong.

But instead, let’s start with the imperial numbers:

55lb is equivalent to 24.943kg

65lb is equivalent to 29.478kg

Ah - now it works.  Presumably my tennis racquet was strung in imperial units which were then converted to metric.

I will try this with a class next week to see if they can work out what is going on. 

And then, if they manage to work it out I will ask them to help me with the tensions on my son’s racquet (which don’t work either way around!).