Normal force facts for kids
The normal force is a special kind of force that a surface pushes back with. Imagine you are standing on the ground. The normal force is the push from the ground that stops you from falling through it! If there was no normal force, you would slowly sink into the ground.
The normal force always pushes straight out from the surface. This means it is always at a right angle (90 degrees) to the surface the object is on.
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Understanding Normal Force
When an object rests on a surface, its weight pushes down. The normal force is the surface pushing back up. This is an example of Newton's Third Law of Motion, which says that for every action, there is an equal and opposite reaction. Your weight pushes down on the floor, and the floor pushes back up with the normal force.
Normal Force on Flat Surfaces
When an object is on a flat, horizontal surface, like a table or the floor, the normal force is usually equal to the object's weight.
For example, if you place a book on a table, the book's weight pulls it down. The table pushes up with an equal normal force. This keeps the book from falling through the table.
We can calculate an object's weight by multiplying its mass by the force of gravity. So, on a flat surface, the normal force is equal to the object's weight.
Normal Force on Slanted Surfaces
Things get a little different when an object is on a slanted surface, like a ramp or a hill. This is called an inclined plane.
On a slanted surface, the normal force is less than the object's full weight. This is because part of the object's weight is pulling it down the slope, not straight into the surface. The normal force only has to support the part of the weight that is pushing directly into the surface.
Think about a car parked on a hill. The car's weight still pulls it straight down towards the Earth. But the normal force from the road pushes straight out from the slanted road surface. This normal force is less than the car's total weight because some of the weight is trying to make the car roll down the hill.
Images for kids
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Figure 2: Weight (W), the frictional force (F'r), and the normal force (F'n) acting on a block. Weight is the product of mass (m) and the acceleration of gravity (g).
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See also
In Spanish: Fuerza normal para niños
