"In a head-on automobile collision, a person's momentum could be reduced from 2000 kg m/s to zero in just 0.1 s. If this occurs, the average force exerted to stop the person is"

20000N

Explanation:

F=m(v-u)/t

F=force

M=mass

T=time

V and U= final velocity and initial velocity respectively.

M(v-u)=2000kg/m/s

T=0.1s

F=m(v-u)/t

F=2000/0.1

F=20000N

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible

no. dot product   =0 when vecs at right angles