Unizor - Physics4Teens - Mechanics - Dynamics - Resultant Force
Channel: Zor Shekhtman on UNIZOR Education
Date: 2018-05-14

Unizor - Physics through a Looking Glass of Mathematician

Notes to a video lecture on http://www.unizor.com

Resultant Force

According to the Principle of Superposition of Forces, we can replace actions of many forces acting upon a point-object (each one being a vector) with a vector sum of these forces (called resultant force), getting exactly the same effect on the motion of a point-object.

An immediate consequence from the Principle of Superposition of Forces is that any single force acting upon a point-object can be replaced by a vector sum of a few forces, which produce exactly the same effect on the motion of a point-object, as long as this vector sum of forces exactly equals to the vector of original force.

We will demonstrate this Principle on a few examples.


Example 1

In the frame of reference associated with the ground we have a point-object sliding down a slope.
Given are: mass of an object m, force of gravitation of this object (its weight, directed vertically down) W and an angle φ between a slope of a slide and horizontal ground.
Our task is to determine the acceleration of this object on its trajectory down a slope, considering there is no friction that slows down the object's movement down a slope.

Example 2

A motorcycle stuntman decides to demonstrate his skills by going inside a vertical loop.
His mass is m.
His linear speed inside this loop is v.
The magnitude of the gravity force (his weight with a motorcycle) is W.
The radius of a loop is R.
Find the pressure on the loop at its top and at its bottom from a moving motorcycle.