# Forces

## Measuring Forces

### In National 5, A Force was measured with a Newton-Balance. A Newton Balance consists of a Spring with an attached scale. As Force is applied, the Spring is extended. ## Balanced Forces

### When two identical Forces act in opposite directions, they cancel each other out. ## Terminal Velocity

### The Air Resistance that they experience is equal in size and in opposite direction to their Weight :- ## Unbalanced Force

### When an object experiences an unbalanced Force, the object will accelerate. This can either be cause by only one Force acting (as in the diagram below), or by two unequal Forces acting in opposite directions. ## Example 1 -

### A Truck of mass 2000 kg is acted upon by two Forces as shown in the diagram below:- ## Motion Case Study : Skydiving

### The following Velocity-Time graph shows the motion of a skydiver during a jump. By observation of the graph, it is possible to identify key times in the jump process :- ## Resultant Vectors

### So far in this section, the focus has been on Forces acting in the same plane, however Forces (and all other Vectors) can act in multiple planes. In order to understand the effect of Forces acting in different planes, the components of the Forces must be found. ### In order to find the components of a vector, Trigonometry can be used. ## Example 1 -

### What are the components in the horizontal and vertical direction of a Force of 35 N acting at an angle of 25° upwards from horizontal ? ## Forces on a Slope ( Frictionless )

### If the surface is tilted at an increasing angle, the object will begin to move. This is because when the slope is at an angle, a component of Weight acts down the slope, causing the object to move. ### By again applying Trigonometry to find the components of the Weight the following can be found :- ## Example 2 -

### A 2 kg block is placed on a slope at an angle of 15° to the horizontal. Calculate the Force acting down the slope, and therefore the Acceleration of the block. ## Forces on a Slope ( With Friction )

### Friction always act in the opposite direction to motion, so in the above example Friction would have acted up the slope, reducing the unbalanced Force, and therefore reducing the Acceleration. ## Example 4 - ### Object A only :- ## Moving in Microgravity

### The diagram below shows a Command module (on the Left) attached to a satellite (on the right):- 