3. 5 m A D C B 0.5 m 1.3 m Figure 2 A beam ADCB has length 5 m. The beam lies on a horizontal step with the end A on the step and the end B projecting over the edge of the step. The edge of the step is at the point D where DB = 1.3 m, as shown in Figure 2. - la When a small boy of mass 30 kg stands on the beam at C, where CB = 0.5m, the beam is on the point of tilting The boy is modelled as a particle and the beam is modelled as a uniform rod. (a) Find the mass of the beam. (3)

the answer is b, have negligible mass

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

the answer you are looking for is d. there are no holes for blood to enter or leave the system. your welcome