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.

The answer to your question is,

B. It is perpendicular to a surface.

-Mabel <3

option (B)

Explanation:

When an object is placed on the table top, then weight of the object acts on the table and the direction of weight is perpendicularly downwards.

The table top gives a normal force to the object. The normal force is always perpendicular to the surface.

In this condition, action force is weight and the reaction force is normal force. they both act on two different bodies.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.

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