Forces Flashcards

1
Q

Scalar quantities

A

Only have magnitude, no direction

E.g. distance, time, power, mass, energy, current, voltage, charge, frequency

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2
Q

Vector quantities

A

Has magnitude and direction

E.g. force, acceleration, momentum, velocity

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3
Q

Contact forces

A

The objects are physically touching

E.g. friction, air resistance

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4
Q

Non-contact forces

A

The objects are physically separated

E.g. gravitational force, electrostatic force

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5
Q

Weight

A

The force acting on an object due to gravity

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6
Q

Weight formula

A

Weight = mass x gravitational field strength

W = m x g

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7
Q

Resultant forces

A

The sum of all forces acting upon an object

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8
Q

Equilibrium

A

When there is no resultant force, therefore forces are balanced

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9
Q

Displacement

A

How far away you are from the original position

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10
Q

Work done formula

A

Work done - force x distance

W = f x d

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11
Q

Force formula

A

Force = spring constant x extension

F = k x e

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12
Q

How forces affect the extension of a spring practical

A

Secure a clamp stand to the bench using a G-clamp

Use bosses to attach two clamps to the clamp stand

Attach the spring to the top clamp, and a ruler to the bottom clamp

Adjust the ruler so that it is vertical, and with its zero level with the top of the spring

Measure and record the unloaded length of the spring

Hang a 100 g mass from the spring and measure the new length of the spring

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13
Q

Turning force / moment formula

A

Force x perpendicular distance

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14
Q

Levers

A

They are force multipliers, they create moments

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15
Q

Gears

A

Allow motion to be transferred from one point to another

They can also increase or decrease the turning force (moment)

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16
Q

Pressure formula

A

Force / area

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17
Q

Pressure in a fluid

A

The pressure in fluids causes a force normal (at right angles) to any surface

18
Q

Pressure in a column formula

A

Pressure = height of the column x density x gravitational field strength

19
Q

Upthrust

A

An object that is submerged experiences a greater pressure on its bottom surface than on its top surface

This causes a resultant force upwards

20
Q

Factors affecting floating and sinking

A

Densities of the object

Densities of the liquid

Force exerted by the object

21
Q

Atmospheric pressure

A

Air molecules colliding with a surface create atmospheric pressure

The number of air molecules above a surface decreases as the height of the surface above ground level increases

So as height increases there is always less air above a surface than there is at a lower height

So atmospheric pressure decreases with an increase in height

22
Q

Speed

A

How fast you are going disregarding direction

23
Q

Speed formula

A

Speed = distance / time

S = d / t

24
Q

Walking, running and cycling speed

A

Walking - 1.5 m/s

Running - 3 m/s

Cycling - 6 m/s

25
Speed of sound in air
330 m/s
26
Velocity
The speed of an object in a particular direction
27
Acceleration
Amount that velocity changes per unit time Gradient of the line
28
Acceleration formula
Change in velocity / time taken ΔV / t
29
Acceleration formula (2)
(final velocity)² - (initial velocity)² = 2 x acceleration x distance
30
Distance travelled on graph
The area under the line
31
Newtons 1st law
Objects with balanced forces acting on them will stay at rest, or in constant motion
32
Newton's Second Law
Force = mass x acceleration
33
Practical 7
34
Newtons 3rd law
Every action has an equal and opposite reaction
35
Stopping distance
Thinking distance + braking distance
36
Factors affecting braking distance
Wet or icy roads Condition of the brakes Speed of the car Mass of the car
37
Factors affecting thinking distance
Tiredness Drugs Alcohol
38
Momentum
Product of mass and velocity
39
Momentum formula
Mass x velocity M x v
40
Conservation of momentum
Total momentum before an event = total momentum after an event E.g. when a gun recoils backwards
41
Change in momentum formula
Change in momentum = force x change in time
42
Safety features in a car
Airbags, crumple zones, seat belts The force of the collision is equal to the rate of change of momentum These different safety features decrease the rate of change of momentum, which decreases the force of the collision on any people within the car