A $4$ kg block starts from rest and is pulled down a $30$ degree incline by applying a

constant $30$ N tension force parallel to the surface. The coefficient of kinetic friction between surface

and block is $0\mathrm{.}2.$ When the block has moved $1\mathrm{.}0$ meter along the incline:

$1.$ The work done by gravity is

a$)20$ J

b$)30$ J

c$)40$ J

d$)50$ J

e$)60$ J

$2.$ The work done by the normal force is

a$)0$ J

b$)10$ J

c$)20$ J

d$)30$ J

e$)40$