Normal force is the amount of force needed to counteract the action of external forces present in a given scenario. To calculate the normal force one must consider the circumstances of the object and the data available for the variables. Read on for more information.
Steps
Method 1 of 5: Normal Strength in Resting Conditions
Step 1. Understand the concept of "normal force"
Normal force refers to the amount of force needed to counteract the force of gravity.
Imagine a block on a table. The force of gravity pulls the block towards the ground, but there is clearly another force at work that prevents the block from crossing the table and crashing to the ground. The force that prevents the block from falling in spite of the force of gravity is, in fact, the Normal strength.
Step 2. Know the equation for calculating the normal force of an object at rest
To calculate the normal force of an object at rest on a flat surface, use the formula: N = m * g
- In this equation, No. refers to normal strength, m to the mass of the object, e g to the acceleration of gravity.
- For an object that is at rest on a flat surface, and not subject to the influence of external forces, the normal force is equal to the weight of the object. In order to keep the object still, the normal force must be equal to the force of gravity acting on the object. The force of gravity acting on the object is represented by the weight of the object itself, or its mass multiplied by the acceleration of gravity.
- "Example": Calculate the normal strength of a block with a mass of 4, 2 g.
Step 3. Multiply the mass of the object by the acceleration of gravity
The result will give you the weight of the object, which ultimately equates to the normal strength of the object at rest.
- Note that the gravitational acceleration at the surface of the Earth is a constant: g = 9.8 m / s2
- "Example": weight = m * g = 4, 2 * 9, 8 = 41, 16
Step 4. Write your answer
The previous step should solve the problem by giving you the answer.
"Example": The normal force is 41, 16 N
Method 2 of 5: Normal Force on an Inclined Plane
Step 1. Use the appropriate equation
To calculate the normal force of an object on an inclined plane, one must use the formula: N = m * g * cos (x)
- In this equation, No. refers to normal strength, m to the mass of the object, g to the acceleration of gravity, e x to the angle of inclination.
- "Example": Calculate the normal force of a block with a mass of 4, 2 g which is on a ramp with a slope of 45 °.
Step 2. Calculate the cosine of the angle
The cosine of an angle is equal to the sine of the complementary angle, or to the adjacent side divided by the hypotenuse of the triangle formed by the slope
- This value is often calculated using a calculator, since the cosine of an angle is a constant, but you can also calculate it manually.
- "Example": cos (45) = 0.71
Step 3. Find the weight of the object
The weight of an object is equal to the mass of the object multiplied by the acceleration of gravity.
- Note that the gravitational acceleration on the surface of the Earth is a constant: g = 9.8 m / s2.
- "Example": weight = m * g = 4, 2 * 9, 8 = 41, 16
Step 4. Multiply the two values together
In order to calculate the normal force, the weight of the object must be multiplied by the cosine of the angle of inclination.
"Example": N = m * g * cos (x) = 41, 16 * 0, 71 = 29, 1
Step 5. Write your answer
The previous step should fix the problem and give you the answer.
- Note that for an object that is on an inclined plane, the normal force should be less than the weight of the object.
- "Example" ': The normal force is 29, 1 N.
Method 3 of 5: Normal Force in Cases of Downward External Pressure
Step 1. Use the appropriate equation
To calculate the normal force of an object at rest when an external force exerts downward pressure on it, use the equation: N = m * g + F * sin (x).
- No. refers to normal strength, m to the mass of the object, g to the acceleration of gravity, F. to the external force, e x at the angle between the object and the direction of the external force.
- "Example": Calculate the normal force of a block with a mass of 4.2g, when a person exerts downward pressure on the block at an angle of 30 ° with a force of 20.9 N.
Step 2. Calculate the weight of the object
The weight of an object is equal to the mass of the object multiplied by the acceleration of gravity.
- Note that the gravitational acceleration on the surface of the Earth is a constant: g = 9.8 m / s2.
- "Example": weight = m * g = 4, 2 * 9, 8 = 41, 16
Step 3. Find the sine of the angle
The sine of an angle is calculated by dividing the side of the triangle opposite the angle by the hypotenuse of the angle.
"Example": sin (30) = 0, 5
Step 4. Multiply the breast by the external force
In this case, the external force refers to the downward pressure exerted on the object.
"Example": 0, 5 * 20, 9 = 10, 45
Step 5. Add this value to the weight of the object
This way you will get the normal force value.
"Example": 10, 45 + 41, 16 = 51, 61
Step 6. Write your answer
Note that for an object at rest on which external downward pressure is exerted, the normal force will be greater than the weight of the object.
"Example": The normal force is 51, 61 N
Method 4 of 5: Normal Force in Cases of Direct Upward Force
Step 1. Use the appropriate equation
To calculate the normal force of an object at rest when an external force acts on the object upward, use the equation: N = m * g - F * sin (x).
- No. refers to normal strength, m to the mass of the object, g to the acceleration of gravity, F. to the external force, e x at the angle between the object and the direction of the external force.
- "Example": Calculate the normal force of a block with a mass of 4.2g when a person pulls the block upward at an angle of 50 ° and with a force of 20.9 N.
Step 2. Find the weight of the object
The weight of an object is equal to the mass of the object multiplied by the acceleration of gravity.
- Note that the gravitational acceleration on the surface of the Earth is a constant: g = 9.8 m / s2.
- "Example": weight = m * g = 4, 2 * 9, 8 = 41, 16
Step 3. Calculate the sine of the angle
The sine of an angle is calculated by dividing the side of the triangle opposite the angle by the hypotenuse of the angle.
"Example": sin (50) = 0.77
Step 4. Multiply the breast by the external force
In this case, the external force refers to the force exerted on the object upward.
"Example": 0.77 * 20.9 = 16.01
Step 5. Subtract this value from the weight
This way you will get the normal strength of the object.
"Example": 41, 16 - 16, 01 = 25, 15
Step 6. Write your answer
Note that for an object at rest on which an external upward force acts, the normal force will be less than the weight of the object.
"Example": The normal force is 25, 15 N
Method 5 of 5: Normal Force and Friction
Step 1. Know the basic equation for calculating kinetic friction
Kinetic friction, or the friction of a moving object, is equal to the coefficient of friction multiplied by the normal force of an object. The equation comes in the following form: f = μ * N
- In this equation, f refers to friction, μ the coefficient of friction, e No. to the normal strength of the object.
- The "coefficient of friction" is the ratio of the frictional resistance to the normal force, and is responsible for the pressure exerted on both opposing surfaces.
Step 2. Rearrange the equation to isolate the normal force
If you have a value for the kinetic friction of an object, and the coefficient of friction of that object, you can calculate the normal force using the formula: N = f / μ
- Both sides of the original equation were divided by μ, thus isolating on the one hand the normal force, and on the other the coefficient of friction and kinetic friction.
- "Example": Calculates the normal force of a block when the coefficient of friction is 0, 4 and the amount of kinetic friction is 40 N.
Step 3. Divide the kinetic friction by the coefficient of friction
This is essentially all that needs to be done to calculate the normal force value.
"Example": N = f / μ = 40/0, 4 = 100
Step 4. Write your answer
If you find it necessary, you can check your answer by putting it back into the original equation for kinetic friction. If not, you will have solved the problem.
