Flashcards in Mechanics Deck (109)

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1

## What is a vector quantity?

### A physical quantity with magnitude and direction.

2

## What is a scalar quantity?

### A physical quantity with only magnitude.

3

## Give three examples of scalar quantities.

###
-Distance

-Speed

-Mass

4

## Give five examples of vector quantities.

###
-Displacement

-Velocity

-Acceleration

-Momentum

5

## When can vector quantities be added together?

### When the vectors are parallel or antiparallel.

6

## How can resultant vectors be calculated?

###
-Scaled diagram

-Pythagoras

-Trigonometry

-Resolve components

7

## How are vectors added using a scaled diagram?

###
-The vectors are drawn to scale and joined head to tail in the correct direction.

-The resultant vector joins the polygon.

8

## What are the components of a vector?

### The perpendicular pair of vectors.

9

## How can vectors be added by resolving components?

###
-The vertical and horizontal components of the vectors are calculated.

-The perpendicular components are added and the resultant vector calculated.

10

## What is the component parallel to the slope of a weight?

### mgsinx

11

## What is the component perpendicular to the slope of a weight?

### mgcosx

12

## Which forces acting on a weight are parallel to the slope?

###
-Friction

-Weight component

13

## Which forces acting on a weight are perpendicular to the slope?

###
-Normal reaction force

-Weight component

14

## What is a moment?

### A force that produces a turning effect given by force x perpendicular distance from the line of action of the force to the pivot.

15

## What is a moment also known as?

### Torque

16

## How can a moment be increased?

###
-Increased force

-increased distance

17

## What is the principle of moments?

### At balance, the sum of the clockwise moments about a point is equal to the sum of the clockwise moments about the same point.

18

## What is the centre of gravity?

### The point from which all the weight of an object appears to from.

19

## Explain how the centre of gravity of a lamina can be found.

###
-Make a small hole in the corner of the shape and suspend it from a pin so it can move freely.

-Hang a plumb line from the pin and mark the vertical line.

-Repeat for two more points.

-The point of intersection shows the centre of gravity.

20

## How can an object be made stable?

###
-Low centre of mass.

-Large base area.

21

## When will an object tip over?

### When the centre of gravity passes outside the base.

22

## What is statics?

### The study of forces acting on stationary objects.

23

## What is Newtonian mechanics?

### The study of objects that obey Newton's three laws of motion.

24

## Define coplanar forces.

### Forces that all act in the same plane.

25

## What happens when the vectors acting on a point form a closed polygon?

### There is no resultant vector.

26

## Give the two conditions for static equilibrium of coplanar forces.

###
-The resultant vector must be zero.

-The principle of moments must apply.

27

## What is the principle of concurrency?

### For three coplanar forces in equilibrium, the lines action must all pass though one point. (be concurrent)

28

## What does the principle of concurrency apply to?

### An object acted on by three forces.

29

## Define dynamics.

### The study of forces that may result in motion.

30