Flashcards in 4.1-4.8 Forces in Action Quizlet Cards Deck (29)

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1

## What is the centre of mass of an object?

### The point at which the weight can be assumed to act.

2

## What does the weight of an object depend on?

### It's mass and the gravitational field strength (W=mg)

3

## What is a free-body diagram?

### It is a diagram showing the set of forces acting on a single object.

4

## What is weight?

### The force due to gravity that acts through an objects centre of mass.

5

## What is friction?

### The force that acts between two surfaces in contact to oppose motion.

6

## What is drag?

### The resistive force that acts on an object moving through a fluid

7

## What is tension?

### The force within a stretched object such as a cable or rope.

8

## What is upthrust?

### The upward buoyant force that acts on an object in a fluid.

9

## What is a normal contact force?

### A force that acts perpendicular to a surface when an object rests on it.

10

## How do you calculate the component of weight down a slope?

### W sin (θ) where θ is the angle between the slope and horizontal.

11

## How do you calculate the component of weight acting perpendicular to a slope?

### W cos (θ) where θ is the angle between the slope and horizontal.

12

## What are the key factors in determining the magnitude of drag force acting on an object in a fluid?

### Speed and cross-sectional area

13

## What is terminal velocity?

### The maximum speed reached by a falling object when drag and weight are equal.

14

## What is a moment?

### The turning effect produced by a force.

15

## What units do moments have?

### Nm

16

## How do you calculate a moment about a point?

### Force x perpendicular distance to the line of action of the force

17

## What is meant by a body being in equilibrium?

### The net force and the net moment acting on the body are both zero.

18

## What is the principle of moments?

### For an object in rotational equilibrium the sum of the clockwise moments about any point is equal to the sum of anticlockwise moments about that point.

19

## What is a couple?

### A pair of equal and opposite forces acting on an object with different lines of action.

20

## How do you calculate the moment of a couple?

### Force x perpendicular distance between the lines of action of the forces.

21

## What is a triangle of forces?

### A vector diagram of the three forces acting on an object in equilibrium.

22

## What is a resultant/net force?

### The vector sum of forces acting on an object

23

## What is the density of a substance?

### mass per unit volume.

24

## What are the units of density?

### kgm⁻³

25

## What is pressure?

### Normal force acting per unit area

26

## What is Archimedes principle?

### The upthrust exerted on an object is equal to the weight of fluid displaced

27

## What is p in the equation p = hρg

### Pressure exerted by a fluid

28

## What is ρ in the equation p = hρg

### Density of the fluid

29