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Mechanics As > Ch:1 > Flashcards

Ch:1 Flashcards

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1
Q

What are the two main types of quantities in physics?

A

Vectors (with magnitude and direction) and Scalars (magnitude only)

Vectors include quantities like displacement and velocity, while scalars include distance and speed.

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2
Q

How is displacement defined?

A

Displacement is the position - displacement from a fixed origin.

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3
Q

What does velocity represent?

A

Velocity is the rate of change of position.

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4
Q

What is acceleration?

A

Acceleration is the rate of change of velocity.

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5
Q

Define speed.

A

Speed is the magnitude of velocity.

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6
Q

What is the formula for average speed?

A

Average speed = total distance travelled / total time taken.

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7
Q

How is average velocity calculated?

A

Average velocity = displacement / time taken.

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8
Q

What is the formula for average acceleration?

A

Average acceleration = change in velocity / time taken.

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9
Q

What does a position-time graph represent?

A

A position-time graph shows the initial position and how position changes over time.

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10
Q

In a velocity-time graph, what does the gradient represent?

A

The gradient represents velocity.

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11
Q

What does the area under a speed-time graph indicate?

A

The area indicates displacement.

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12
Q

What is the relationship between vertical and horizontal motion?

A

Vertical is towards the centre of the earth; horizontal is perpendicular to vertical.

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13
Q

True or False: In a distance-time graph, the gradient represents speed.

A

True.

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14
Q

Fill in the blank: Average speed is calculated by dividing total distance travelled by _______.

A

[total time taken].

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15
Q

What does a negative displacement indicate?

A

A negative displacement indicates movement in the opposite direction.

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16
Q

In terms of motion, what happens when speed increases?

A

When speed increases, acceleration is positive.

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17
Q

What happens to speed when acceleration is negative?

A

Speed decreases.

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18
Q

What are the formulae for motion with constant acceleration?

A

v = u + at, s = ut + ½at², v² = u² + 2as, s = vt - ½at²

Where v is the final velocity, u is the initial velocity, a is the constant acceleration, s is the displacement, and t is time.

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19
Q

What does the variable ‘a’ represent in the suvat formulae?

A

Constant acceleration

Acceleration is the rate of change of velocity.

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20
Q

How is the displacement ‘s’ defined in the suvat equations?

A

Displacement from the starting position at time t

s can be adjusted if the starting position is not zero.

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21
Q

What is the typical value of acceleration due to gravity (g) used in calculations?

A

10 m/s²

The more precise value of g is 9.8 m/s².

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22
Q

What direction does the acceleration due to gravity act?

A

Vertically downwards

This is important when analyzing vertical motion.

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23
Q

What is a key consideration when drawing a diagram for motion problems?

A

Decide where your origin is and which way is positive

This helps in accurately defining the motion’s direction.

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24
Q

What must be ensured regarding units when solving motion problems?

A

Units must be compatible

This is crucial for accurate calculations.

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25
What is an example of a simplifying assumption when modeling a car in motion?
A car is a particle with no dimensions ## Footnote This simplifies analysis by reducing complexity.
26
What is the first step in using a mathematical model for motion?
Make simplifying assumptions ## Footnote This helps in focusing on the most relevant aspects of the problem.
27
What should be done after setting up equations in a mathematical model?
Solve the equations ## Footnote This leads to finding the desired quantities.
28
What is important to check after obtaining a solution in a mathematical model?
Check that the answer is sensible ## Footnote If the answer seems unreasonable, re-evaluate the assumptions or calculations.
29
What are force diagrams used for?
Understanding most mechanical situations ## Footnote Force diagrams visually represent forces acting on an object.
30
What are the three essential components that a force diagram should show?
* Direction of the force * Magnitude of the force * Line of action ## Footnote These components help in analyzing the forces acting on an object.
31
True or False: A force is a vector that has only magnitude.
False ## Footnote A force also has direction and a line of action.
32
In a force diagram, how is air resistance typically depicted?
By multiple separate arrows ## Footnote However, it is often better to show the combined effect with one arrow.
33
What does the line of action in a force diagram indicate?
The path along which the force acts ## Footnote This line often passes through a point of particular interest in the system.
34
Fill in the blank: A force has a _______ and a direction.
magnitude ## Footnote The magnitude refers to the size or strength of the force.
35
What can be combined into one force in a force diagram?
Tensions in the guy lines ## Footnote This simplification aids in the analysis of forces on objects.
36
What is depicted by arrows in force diagrams?
Each force along its line of action ## Footnote The length of the arrow typically represents the magnitude of the force.
37
What forces are acting on a parachute as shown in the diagrams?
* Weight of parachute * Air resistance * Combined tension ## Footnote These forces are represented in the force diagram for the parachute.
38
What forces are acting on a crate as shown in the diagrams?
* Weight of crate * Air resistance on crate * Combined tension ## Footnote These forces are represented in the force diagram for the crate.
39
What is the resultant when combining forces?
The resultant is the sum of all individual forces acting on an object.
40
What is the centre of mass?
The centre of mass is the point through which the total weight of an object acts.
41
What happens when a pen is balanced on a finger under its centre of mass?
The pen will balance and the forces are in equilibrium.
42
What is required for an object to be in equilibrium?
The forces must have the same line of action.
43
What occurs if the finger is placed under a point other than the centre of mass of the pen?
The pen will fall.
44
When balancing a pen on two fingers, what can be said about the reactions between each finger and the pen?
The reactions can be combined into one resultant vertical reaction acting through the centre of mass.
45
What does Mechanics 1 focus on regarding forces?
Mechanics 1 deals with situations where the resultant of the forces does not cause rotation.
46
How is an object modeled in Mechanics 1?
An object is modeled as a particle, or point mass, situated at its centre of mass.
47
Who is Sir Isaac Newton?
Sir Isaac Newton (1642-1727) is known for his work on gravity and Newtonian Mechanics.
48
What are Newton's three laws of motion used for?
They provide a model for how objects behave when influenced by forces.
49
Fill in the blank: Newtonian Mechanics is based entirely on _______.
[Newton's three laws of motion]
50
True or False: The behaviour of objects that rotate under the action of forces is covered in Mechanics 1.
False.
51
What is the significance of Newton's laws of motion?
They model the behavior of objects from specks of dust to planets and stars.
52
What always acts in a direction opposite to the velocity of a vehicle or boat?
Resistances due to air or water ## Footnote These resistances are usually more significant for fast-moving objects.
53
What forces act on the crate of supplies and the parachute connected by lines?
Tension forces ## Footnote The lines pull upwards on the crate and downwards on the parachute.
54
What happens to the forces on your hands when you pull a pencil apart?
The forces on your hands are outwards and the pencil is in tension ## Footnote This is illustrated in a diagram showing tension forces.
55
What occurs when you push a pencil inwards?
The pencil is in compression and the forces on your hands are outwards ## Footnote The outward force on each hand is called a thrust.
56
If each hand applies a force of 2 units on the pencil, what is the tension or thrust acting on each hand?
2 units ## Footnote This is because each hand is in equilibrium.
57
What is the equivalent of several forces acting together?
A single force called the resultant force ## Footnote This can be illustrated with a scenario of people pushing a car.
58
What happens when there is no resultant force?
The forces are in equilibrium and there is no change in motion.
59
What are the forces acting on a car using a tow bar to pull a trailer?
Resisting forces R on the car, S on the trailer, driving force D, and braking force B ## Footnote These forces vary depending on the car's motion.
60
What is the state of the tow bar when the car moves at constant speed?
The tow bar is in tension ## Footnote This creates a forward force on the trailer and an equal backward force on the car.
61
Fill in the blank: The pencil is in _______ when you push it inwards.
compression
62
True or False: The forces on your hands are inwards when the pencil is in tension.
True
63
When the car is accelerating, what happens to the resultant force acting on it?
The resultant force is positive and greater than the resisting forces.

Mechanics As (1 decks)

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