Worked example A uniform wooden lath AB, 120 em long and weighing 1.20 N rests on two sharp-edged supports C and D placed 10 cmfrom each end of the lath respectively. A 0.20 N weight hangs from a loop of thread 30 em from A and a 0.90 N weight hangs similarly 40 em from B. Find the […]
Stable unstable and neutral equilibrium A child playing with a pencil soon learns that it is scarcely possible to make it balance on its point. On the other hand, it is comparatively easy to make the pencil stand upright on a flat end.In order to understand the difference between these two cases let us consider a wooden cone placed […]
The steelyard The steelyard is a weighing device which has been used since Roman times. It is particularly suitable for weighing objects which can be suspended from a hook, e.g., sacks of farm produce and car-cases of meat. It consists of a graduated steel rod pivoted near one end and balanced by a heavy piece of metal B (Fig. […]
To measure the mass of a metre rule by using a single known mass A metre rule is supported in a loop of thread hung from a clamp and stand and dusted until it balances horizontally. The loop will then be at the centre of gravity, G. of the rule. If the rule is not of uniform thickness […]
Principle of the. beam balance We are now able to explain the principle of the beam balance, the construction which was discussed in chapter I, The unknown mass m1, is placed in the left-ha pan and standard masses, rn-, are placed in the right-hand pan to obtain equilibrium (Fig. 6.1 0). The balance has been constructed so that the […]
To find the mass of an object by means of a metre rule A metre rule with a small hole drilled near its centre as described on page 62 can be used in conjunction with a single known mass to measure the mass of an object. Having balanced the rule on a knitting needle as described on […]
Centre of gravity of a stool or tripod Sometimes the centre of gravity of a body is not situated in the actual material of the body, but may be at a point in the air near by. Examples are an iron tripod or a Laboratory stool. The plumbline method can still be employed, but requires more will […]
To locate centre of gravity by means of a plumbline One of the best ways of finding the centre of gravity of a body is by use of a plumbline. Suppose, for example, we wish to find the centre of gravity of a flat irregularly shaped piece of cardboard. First of all, three small holes are made at […]
To locate centre of gravity by a balancing method The centre of gravity of a long thin object such as a ruler or billiard cue may be found approximately by simply balancing it on a straight-edge. The same method could also be used for a thin sheet or lamina of cardboard or metal, except that in this case […]
The plumbline When a body is freely suspended by a string and is at rest the force of gravity on it, acting vertically downwards, is balanced by an equal and opposite force or tension in the string. Being flexible, the string therefore sets in a vertical direction. This is the principle of the plumbline, which consists of a […]