There is two match officials carry an injured rugby player from a rugby field on a stretcher. The rugby player weighs 95kg and the stretcher is 2.5 m long. One of the stretcher-bearers (bearers A) is able to lift a weigh of 60kg; the other (bearer B) is unsure how much weight he is able to lift.
(a) How much weight must bearer B support?
(b) How far from bearer A must the injured rugby players center of mass be in order for the stretcher-bearers to load without tipping the injured player out?
4.9 Two match officials carry an injured rugby player from a rugby field on a stretcher. The rugby player weighs 95 kg and the stretcher is 2.5 m long. One of the stretcher bearers (bearer A) able to lift a weight of 60 kg; the other (bearer B) is unsure how much weight he is able to lift.
To find the weight that bearer B must support, we can subtract the weight that bearer A can support from the total weight of the rugby player.
(a) Weight supported by bearer B = Total weight of rugby player - Weight supported by bearer A
= 95 kg - 60 kg
= 35 kg
Therefore, bearer B must support 35 kg of weight.
Now let's move on to part (b) and determine how far from bearer A the injured rugby player's center of mass must be in order to avoid tipping.
For the stretcher to remain balanced and not tip, the center of mass of the system (combination of the rugby player and the stretcher) must be located within the base formed by the two bearers.
The base formed by the two bearers can be considered as a rectangle with bearer A at one end and bearer B at the other end. The length of this rectangle is the distance between the bearers, which is 2.5 m.
To avoid tipping, the center of mass must be located within this rectangle. Since the rugby player's weight is evenly distributed along their body, the center of mass can be assumed to be halfway between bearers A and B.
The distance from bearer A to the center of mass is therefore half the distance between the bearers, or 2.5 m / 2 = 1.25 m.
Therefore, the injured rugby player's center of mass must be 1.25 meters from bearer A in order for the stretcher-bearers to load without tipping the player out.