PHYSICS 1D03 Lecture 7: newton's laws of motion, friction

How many members are in the photon family?


a.
4

b.
2

c.
5

d.
3

e.
1

Three long wires, each carrying current i are placed parallel to each other. The distance between I and II is 3d, between II and III is 4d and between III and I is 5d. Magnetic field at side of wire II is__.

Two uniform solid spheres have the same mass, but one has twice theradius of the other. The ratio of the larger sphere's moment ofinertia to that of the smaller sphere is
a) 4
b) 2
c) 4/5
d) 8/5

please explain answer as best you can. thanks!