How Do You Calculate Normal Force and Work Done in Physics Problems?

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SUMMARY

The discussion centers on calculating the normal force, gravitational force, and frictional force for a 52 kg box pushed 7.0 meters with a force of 149 N and a coefficient of kinetic friction of 0.25. The normal force is calculated as 509.6 N, which equals the gravitational force acting on the box. It is established that the normal force is considered positive, while the gravitational force is typically negative in a coordinate system where downward is negative. Additionally, the distinction between Newtons (force) and Joules (energy) is clarified, emphasizing that they are different units and cannot be directly converted.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Basic knowledge of force and friction concepts
  • Familiarity with units of measurement: Newtons and Joules
  • Ability to perform basic calculations involving mass and acceleration due to gravity
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  • Learn how to calculate work done using the formula W = F × d
  • Study the effects of friction on motion in physics
  • Explore the concept of net force and its implications in various scenarios
  • Investigate the relationship between force, mass, and acceleration in different contexts
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Students studying physics, educators teaching mechanics, and anyone interested in understanding the principles of force and motion in real-world applications.

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52 kg box is pushed 7.0 meters by a force with a magnitude of 149 N. The coefficient of kinetic friction is 0.25. Determine normal force, force of gravity and frictional force.

For the normal force I have 52 * 9.8 = 509.6 N Which is also the the force of gravity. However which is positive and which is negative? I assume normal force is positive since it pushes up against gravity pushing downward? Also, how would I convert Newtons into Joules?
 
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LostInScience said:
52 kg box is pushed 7.0 meters by a force with a magnitude of 149 N. The coefficient of kinetic friction is 0.25. Determine normal force, force of gravity and frictional force.

For the normal force I have 52 * 9.8 = 509.6 N Which is also the the force of gravity. However which is positive and which is negative? I assume normal force is positive since it pushes up against gravity pushing downward? Also, how would I convert Newtons into Joules?
As long as you are consistent, it doesn't matter which direction is positive or negative. Generally, down is usually taken as negative. Now don't confuse Newtons, a unit of force, with Joules, a unit of energy or work. How much work does each force do on the box?
 

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