Chapter 4 Forces in Action Flashcards Preview

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Flashcards in Chapter 4 Forces in Action Deck (24)
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1
Q

What is the equation for force?

A

Force = Mass x Acceleration

2
Q

What is the equation to find weight?

A

Weight = Mass x Force of gravity

3
Q

What is weight?

A

It is the amount of Newtons of force that the earth is attracting the object

4
Q

What is the centre of mass?

A

This is the position at which all the mass of an object appears to be

5
Q

What is the centre of gravity?

A

This is the position at which all the weight of the objecct appears to be

6
Q

What is the method / experiment to find the centre of gravity?

A
  1. Hang the object from a point that is off centre
  2. Draw a line vertically down from the point. Use a guide to help you know where to draw the line (e.g. a weight on a string).
  3. Repeat steps 1 and 2 until all the points cross at one point. This point is the centre of gravity
7
Q

Name some important forces that can act on an object

A
Weight
Friction
Drag
Tension
Upthrust
Normal contact force
8
Q

What is a free-body diagram?

A

It is a diagram that isolates and shows all the forces acting on an object

9
Q

What are the two factors that affect the drag force of an object?

A

The speed and the cross-sectional area

10
Q

What is terminal velocity?

A

This is when the force of the weight moving the object through a fluid is equal to the drag force exerted on the object

11
Q

What is a moment?

A

This is turning force of an object

12
Q

What is the equation of a moment?

A

Moment = Force x perpendicular distance of the line of action of force from axis or point of rotation

13
Q

What is the principle of moments?

A

When in equilibrium, the magnitude of the clockwise force is equal to the magnitude of the anticlockwise force

14
Q

What is a couple?

A

This is the pair of forces acting on an object that rotates around a pivot point. The two forces must be parallel and along different lines.

15
Q

What is the equation for a couple?

A

Moment = (F1 x d/2) + (F2 x d/2)
or if F1 and F2 are equal
Moment = F x d

16
Q

How can the resultant force be calculated?

A

By drawing the forces tip to tail and using trigonometry to work out the resultant force

17
Q

What is density? What is the equation?

A

It is the mass per unit volume.

ρ = m / v

18
Q

How can the exact volume of an object be easily calculated?

A

Place the object in water and work out the change in the level of the water. Use this to work out the volume which is equal to the volume of the object.

19
Q

What is the equation of pressure?

A

Pressure = Force / Cross-sectional area

20
Q

What are fluids?

A

Gasses and liquids

21
Q

What is the equation to work out the pressure exerted by a vertical column of liquid?

A
p = hρg
h = height of water above object
ρ = density of the liquid
g = force of gravity
22
Q

What is upthrust?

A

This is the force pushing an object up through a liquid

23
Q

What is the equation for upthrust?

A

Upthrust = Axρg
A = Cross sectional area of the object placed in the fluid
x = The depth of the object placed in the fluid
So ax is the volume of the object placed in the fluid
ρ = the density of the fluid
g = The force of gravity on the fluid the object is submerged in

24
Q

What is archimedes principle?

A

The upthrust on an object is equal to the weight of the volume of fluid that it displaces