2.4 Forces and Its Effects
Forces
- Forces can change the speed, direction, shape, or size of an object
Newton’s First Law:
An object will either remain at rest or continue to move at a constant speed in a straight line unless acted on by a resultant force
This is also known as the law of inertia
The greater the mass of an object, the greater its inertia, meaning it resists changes to its state of motion more
- To find the resultant force when multiple forces act along the same line, simply add their magnitudes
- Consider the direction: if forces are in the opposite directions, subtract their magnitudes
- When multiple forces are acting at angles, the parallelogram of forces method or trigonometric functions can be used to calculate the resultant force
- Example: If two forces of 5 N and 3 N are acting in the same direction on an object, the resultant force is 8 N. If they act in opposite directions, the resultant force is 2 N
Solid Friction: Friction between two solid surfaces can impede motion and produce heat. It acts in the direction opposite to the motion
Drag: Friction (drag) that acts on an object moving through a fluid (e.g., air or water). Air resistance and water resistance are common examples of drag forces. The magnitude of drag increases with the speed and surface area of the object
- Reducing Friction: Friction can be reduced by using lubricants, streamlining shapes, or using rollers and bearings
Equation:
F = ma
F is the resultant force applied to the object
m is the mass of the object
a is its acceleration
- This law states that the acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass
- A resultant force can change the velocity of an object by changing its direction or speed
- If the resultant force is zero, the object will maintain its current state of motion
- The direction of the acceleration is always the same as the direction of the resultant force