If an object has two forces acting on it, how can the net force equal 0?

Check explanation.

Explanation:

Net force is essentially the sum of the forces enacting upon an object. One example of net force is gravity and normal force. It is commonly accepted that every object has a force acting upon it, even if it is stationary. To give an example, the weight of an object has a force upon the earth but the earth pushes back, essentially meaning that the object will not sink.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.