Juanita studies several free-body diagrams in which a normal force is shown. what is always true about a normal force in a free-body diagram?
a. it is opposite the weight.
b. it is perpendicular to a surface.
c. it is opposite the net force.
d. it is parallel to a surface.

Need only answer if you think you know it

On a horizontal frictionless surface, a small block with mass 0.200 kg has a collision with a block of mass 0.400 kg. immediately after the collision, the 0.200 kg block is moving at 12.0 m/s in the direction 30° north of east and the 0.400 kg block is moving at 11.2 m/s in the direction 53.1° south of east. use coordinates where the +x-axis is east and the +y-axis is north.(a) what is the total kinetic energy of the two blocks after the collision (in ) what is the x-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your ) what is the y-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your answer.)

Which of the following forces require physical contact? tension air resistance friction magnetic force applied force