The net force is the vector sum of these forces. Remember, tho', vector notation is always elegant shorthand notation. The crate has a horizontal acceleration equal to the tension T divided by m, the mass of the crate. The upward normal force exerted by the floor on the crate, in this situation, is equal to the weight, the downward force of gravity. Draw in all the forces.
Gravity exerts a force downward, called the weight and labeled w .
In this example, tho', nothing happens in the horizontal direction. We can use Newton's Laws to determin the value of the normal force. Tension T acts upward on the lamp while the force of gravity pulls down with force w , the weight of the lamp. The net force is the vector sum of these two forces. The lamp is not accelerating so the force up must equal the force down .