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P5-Forces Flashcards

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1
Q

What is the differences between scalar and vector and how is vector represented

A

Scalar-quantity with only magnitude (size)
Vector-a quantity which has magnitude and direction

Represented as arrows direction shows direction length shows magnitude

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2
Q

Give some examples of scalar and vector quantities

A

Scaler-speed, distance, time, energy
Vector -velocity, displacement, acceleration force momentum

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3
Q

What are the differences between contact and noncontact forces? Give some examples

A

Contact forces are physically touching-friction, air resistance, tension

Noncontact forces, are physically separated -magnetic forces, electrostatic forces gravitational forces

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4
Q

What is the equation for weight?

A

Weight= mass x gravitational field (g)
Strength
(N). (Kg). (N/kg)

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5
Q

What is weight?

A

The weight of an object is the force acting on it caused by gravity. Depends on the gravitational field strength. Weight is directly proportional to the mass of the object. Measured using a newton meter or a calibrated spring balance. Wait acts at a single point of an object. (centre of mass)

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6
Q

What is the resultant force?

A

A single force which has the same effect as all the original forces acting together

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7
Q

How can a resultant force acting on an angle be resolved?

A

It can be resolved into two components acting at right angles to each other.
One vertical one horizontal coming from each point of the arrow. Make sure all is connected.

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8
Q

How do you workout the resultant force using two forces are right angles to each other

A

Use a ruler to measure and draw horizontal and vertical arrows
Draw line to connect
Measure of the line
E.g. 80 cm equals 8 N

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9
Q

What is a Freebody diagram?

A

Use in situations where several forces act on an object
A longer arrow shows that the resultant force is acting in that direction

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10
Q

What happens if forces are balanced

A

If forces are balanced, there is no resultant force, and therefore the object moves at a constant speed or remains stationary

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11
Q

When is work done by force?

A

A force does work on an object when it causes it to move through a distance

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12
Q

What is the equation for work done?

A

Work done = force x distance
W. =. F. X. S
(J). (N). (M)

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13
Q

What happens when work is done and what is joule equal to

A

Work done against friction increase the temperature?

1J=1NM

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14
Q

What is required to change the shape of a stationary object and what is it called?

A

To change the shape of a stationary object there must be more than one force acting on the object.

Changes in shape = deformation

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15
Q

What is elastic deformation and example?

A

Reversed when force is removed-elastic band, slightly stretched

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16
Q

What is inelastic deformation and example

A

Not fully reversed when forces removed
There has been a permanent change in shape
Plastic bottle that is squashed

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17
Q

What is Hookes law?

A

The extension of an elastic object is directly proportional to the force applied (provided the limit of proportionality is not exceeded)

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18
Q

What is the equation for force?

A

Force = spring constant (k) x extension
(N). (N/m). (m)

Also applies to compression but e it’s not the amount the object has been compressed

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19
Q

How can we work out the spring constant using a graph?

A

Force on Y axes extension on X axes

Calculate K as gradient

Change in y / change in X

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20
Q

What is the limit of proportionality?

A

When Hookes law is no longer obeyed, and extension is not directly proportional to force

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21
Q

What is elastic limit?

A

The Lasik limit is the furthest point of material can be deformed and still return to its original shape when the force is removed-when this is past defamation is inelastic

(on a graph this is where the line is no longer linear)

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22
Q

What happens when a spring is compressed by force? What is stored in the spring?

A

Work is done on the spring and elastic potential energy is stored in the spring

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23
Q

What is the equation for elastic potential energy?

A

E= 1/2 x k x e squared
(J). (N/M). (M)

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24
Q

What happens if a spring has no inelastic deformation

A

We can say that work done is equal to the elastic potential energy

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25
What are the three parts of the lever and what is it used for?
Pivot Effort-point where force is applied Load-weight of contents Allows us to lift heavy load then effort force would normally allow . Longer leavers increase force exerted on the Load.
26
What is a moment?
Rotate if a force is exerted on it. The moment of a force is the turning affect of a force.
27
What is the equation to calculate the size of the moment
Moment=force x perpendicular distance (NM). (N). (M) (perpendicular distance from the pivot to the line of action of the force
28
What happens when there is a balance object in equilibrium?
The total anticlockwise moment about the pivot = the total clockwise moment about the pivot
29
What is a gear and how do they work?
Gears are wheels with toothed edges. The teeth of one gear is able to connect to the teeth of another gear as one gear turns around one axle. The other gear will also turn. connected gears rotate in opposite direction. Clockwise and anticlockwise.
30
What is a fluid?
A substance that can flow, liquid or gas.
31
What happened to pressure in fluids?
Pressure in fluids causes of force at a right angle (normal) to a surface
32
What is the equation for pressure in fluids?
Pressure= force normal to surface/ area of surface Pressure-pascals (pa) Force-newtons Are-m squared
33
What is a equation of pressure caused by column of liquids?
Pressure= height of column x Density of liquid x gravitational field strength Pressure-pascals Height-m Density- kg/ m cubed Gfs-N/kg
34
What happens when an object is partially or completely submerged in fluid
Experiences a greater pressure on it bottom, then its top. This pressure difference creates an upward resultant force. (Upthrust). If the weight of the object is greater than its upthrust, it will think. If the weight is equal. It will float
35
What decides whether an object sinks or floats
Depends on the density of the object. The upthrust of an object in fluid is equal to the weight of the fluid that it displaces. If the object is more dense than the fluid, it sinks because the weight of the object is greater than the weight of the fluid displaced (greater than upthrust) If the object is less dense than the fluid it floats to the top, because the weight of objects less than the weight of fluid displaced (upthrust)
36
Why is water released a different pressures from a column?
Water from the bottom of the column will spit out at higher pressure and travel farther than water at the top. Pressure in a column of water depend on the height, so how much water is above it.
37
What causes atmospheric pressure?
Air Molecules colliding with surfaces . As height increases fewer air, molecules are above surface. . Density of air decreases as altitude increases. . Weight of air above surface decreases with altitude
38
What is the difference between distance and displacement?
Distance tells us how far object has moved not direction. displacement tells us both
39
What is the average speed of walking running cycling and sound in air And Car train plane
Walking= 1.5 m/s Running = 3 m/s Cycling = 6 m/s Speed of sound in air- 330 m/s Car-25m/s Train-30m/s Plane-250m/s
40
What does speed depend on?
It is scalar. Depends on the age fitness distance travelled terrain
41
What happens when an object moves in a circle at constant speed?
Direction of its motion constantly changes, meaning velocity is also constantly changing because it’s a vector. Magnitude stays the same distance, changes the velocity changes.
42
What is the equation for distance?
Distance (s) = speed (v) x time (t) Metres M/S Seconds
43
When is the distance time graph used?
When an object moves along a straight line Gradient is speed. If the graph is a straight line, the object is moving at a constant speed . The steeper, the line, the faster, the speed. If a curve slopes upwards -accelerating If a curve slopes downwards -decelerating Draw tangent at time being asked about on curve, make triangle, change in y / change in x
44
What is equation for acceleration?
Acceleration= change in velocity / time taken Delta v (M/s squared) (M/s) (S)
45
What are the key facts about a velocity time graph?
Gradient= acceleration Straight line = constant acceleration Steeper line, greater acceleration Curve= acceleration changing Horizontal line= constant velocity Area underline = distance, travelled breakdown into shapes Curved lines = count, Squares under
46
How is terminal velocity reached?
An object, moving through a fluid will initially accelerate due to the force of gravity Over time resistive forces will increase Eventually force of gravity will equal to resistive forces The resultant force equal zero Terminal velocity is reached (constant)
47
How do you velocity time graph show terminal velocity
Resistive forces increased, but weight stays the same Resultant force and acceleration decreases Resistive force is now equal to the weight so resultant forces and acceleration are zero
48
What is Newton’s first law?
If resultant force on a stationary object is zero, the object will remain stationary or the object will continue, moving in the same direction with the same speed When object moves at a constant speed, driving forces are balanced by resistive forces, such as friction, and air resistance
49
What is newton second law?
Acceleration of an object is directly proportional to the resultant force acting on the object and inversely proportional to mass of object
50
What is the equation for resultant force?
Resultant force= mass x acceleration (N) (Kg) (m/s squared)
51
What is inertia?
The tendency of an object to continue in their state of rest, or of uniform motion
52
What is inertial mass?
A measure of how difficult it is to change velocity of an object ratio of force over acceleration
53
What is Newton’s third law?
When two objects interact, the forces day, exert on each other, equal in magnitude, but opposite in direction
54
What is the equation for stopping distance?
Stopping distance= thinking distance+ braking distance Thinking distance -distance to vehicle travels during the drivers reaction time Braking distance-distance to vehicle travels under the braking force Greatest because the greatest stopping distances
55
What is the typical reaction time of a human and what can affect this?
0.2s-0.9s Drugs, tiredness, alcohol distractions
56
Reaction time, practical
Ruler drop practical to find distance travelled by ruler Calculate to find velocity V squared= U squared +2as a=9.8m/s squared (U stands for velocity rearrange) Calculate time taken Acceleration = change in velocity / time Carry on repeat and calculate mean
57
What can affect breaking distance?
Poor Road or weather conditions Poor vehicle conditions
58
What happened to stopping distance if velocity double
If velocity doubles, the stopping distance to increase by factor of four
59
How do we achieve a greater deceleration and what are the dangers?
When force applied to break, work is done Friction between the tires and brake pads cause kinetic energy of vehicle to decrease, and brake pads to increase in temperature The fastest vehicle travels = the greater braking force required = greater deceleration Dangers -breaks can overheat, driver may lose control of vehicle
60
What is momentum, and how to calculate the momentum of an object of mass travelling at velocity
Momentum of the property of moving objects Momentum = mass x velocity ( kg m/s). (Kg). (M/s)
61
What is the conservation of momentum in a closed system?
The total momentum before an event = the total momentum after the event When moving in opposite directions (towards each other) use one velocity as a negative value Eg left arrows= negative right arrows-posit
62
What happens when there is a collision?
When there is a collision, there is a change in momentum The force exerted in a collision = the rate of change of momentum
63
What is equation for force?
Force= change in momentum / time taken Force=newtons Time=seconds Mass= kg Change in velocity= m/s (Momentum= massxchange in velocity)
64
What is the aim of safety features in a car and some examplez
Their aim is to increase the duration of change in the momentum to decrease the force ( same momentum over greater time so less force) Crumple zone , seatbelt, airbags
65
How does a crumpled zone help decrease the force?
. Car crumples on impact. . Increases duration of collision. . Chang in momentum remains the same. . decreases rate of change in momentum. . this decreases force
66
What is the practical to investigate the link between force and extension?
1. Measure the natural length of the spring with a millimetre ruler clamp to a stand.-read at eyelevel 2. Add a mass to the springs. Record mass and measure the new length of the spring extension is change in length 3. repeat until wide range of data. 4. Plot force extension graph. It will come if you exceed the limit of proportionality
67
How to investigate mass and force affect acceleration
1. Attached toy car to piece of string which is looped around a pulley and 100g mass 2. Draw chalk lines on the table at equal intervals 3. Let car go from starting point 4. Record time the car passes each distance marker (record practical on ipad if car is moving rapid) 5. Repeat experiment several times decreasing mass at the end of the string each time (the object is the toy car, string and mass as they are all attached- when you remove mass from end, place on top of toy car to keep total mass the same) Force is weight at the end of the string
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