4 - Forces in Action Flashcards

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1
Q

Energy transfers examples

A

heating (thermal), electrical, light, sound, kinetic forces (mechanical work), nuclear (radiation)

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2
Q

Energy stores examples

A

gravitational potential, chemical potential, thermal store, elastic potential, nuclear potential, magnetic potential, kinetic store

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3
Q

Contact forces

A

air resistance, friction, upthrust, tension, compression, thrust

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4
Q

Non-contact forces

A

weight, electrostatic, magnetic

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5
Q

4 Fundamental forces

A

gravitational (acts on anything with mass e.g. protons, neutrons, electrons), electrostatic/electromagnetic, (acts on anything with charge e.g. protons, electrons), weak nuclear, strong nuclear

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6
Q

If resultant force acting on an object is 0…

A

object is stationary or remains at constant speed as forces are balanced

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7
Q

Centre of mass

A

The point at which an object’s mass is centred or concentrated, the point through which a single force on the body has no turning effect. For regular symmetrical objects, the COM is the centre of the object

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8
Q

Centre of gravity

A

Weight is caused by the attraction of every atom inside an object to every atom inside the Earth. The sum of all of these forces appear to act from a single point for any object, this is the centre of gravity

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9
Q

How to find COM for irregular objects

A

First, make a hole in the material and hang. Hang a piece of string from it with a weight on the end so you can trace the line (plumb line). Make another hole in a different place and do the same thing. Where the lines cross is the centre of mass for that object

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10
Q

What factors affect stability

A

width of base and height of centre of mass. More stable objects have wide bases and low COMs

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11
Q

What is a moment?

A

the turning effect of a force and will act around a pivot. A moment can act clockwise or anticlockwise

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12
Q

Moment equation

A

Moment = Fd
Moment (Nm) = Force (N) x perpendicular distance to the line of action of the force (m)

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13
Q

If a body is in equilbrium…

A

turning force resultant force is 0, the sum of the clockwise moments is equal to the sum of the anti-clockwise moments (CW=ACW

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14
Q

Stable equilibrium:

A

If a body is displaced from the equilibrium position then released, it will return to the equilibrium position

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15
Q

Unstable equilibrium:

A

If a body is displaced from the equilibrium position then released, it will not return to the equilibrium position.

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16
Q

Principle of moments

A

For a body in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about that same point.

17
Q

What is a couple?

A

two equal and opposite forces acting on a body but on different lines of action

18
Q

Density is

A

the amount of mass per unit volume measured in kgm^-3. It is an intrinsic property

19
Q

Density equation

A

Density = mass (kg) /volume (m^3)

20
Q

When will an object float in water?

A

if its density is lower than water (1000kgm^-3)

21
Q

Upthrust

A

the weight of the fluid displaced or the difference in pressure between the top and bottom of an object

22
Q

Effect of volume on upthrust

A

Bigger the volume, bigger the upthrust as they are directly proportional (object material doesnt matter but material submerged in does)

23
Q

Archimedes’ Principle

A

upthrust acting on an object is equa to the weight of the fluid displaced