F.4PHY moment10marks!!!

(a) Moment given by the weight = 1 x 0.25 Nm = 0.25 Nm

(b) Taking moment about the pivot,
cloclwise moment given by the 1 N weight = 1 x 0.25 Nm
anticlockwise moment given by the ball bearings = Wb x 0.2 Nm

where Wb is the weight (in N) of the container of ball bearings.
At equilibrium, the two moments must be the same
hence, 1 x 0.25 = 0.2Wb
Wb = 0.25/0.2 N = 1.25 N

(c) Since there are 100 number of ball bearings, with weight of 1.25 N
weight of a ball bearings = 1.25/100 N = 0.0125 N
mass of a ball bearing = 0.0125/10 kg = 0.00125 kg = 1.25 gram
(since it is given in the question that 1 kg has a weight of 10 N)

(d) End A would tip up. It is because the new ball bearings are of identical size (i.e. same volume) but with lower desnity, hence the mass and weight of the ball bearings are smaller than before. The moment given by the lower density ball bearings is now insufficient to balance the moment given by the 1 N weight at end B of the beam. This causes end A to tip up.