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Physics > Mechanics > Flashcards

Mechanics Flashcards

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1
Q

Define scalar and vector quantities

A

scalar quantities have magnitude only, vector quantities also have a direction

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2
Q

How is a vector resolved?

A

split it into two components at right angles to each other

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3
Q

What do arrows on a free-body diagram represent?

A

direction and size of the forces acting on an object

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4
Q

What is an object in equilibrium

A
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5
Q

What is an object in equilibrium?

A

object at rest or moving with constant velocity

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6
Q

Define the moment of a force about a point

A

moment = force x perp distance from the point to the line of action of the force

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7
Q

What is the principle of moments?

A

for equilibrium, sum of clockwise moments about a point = sum of anticlockwise moments about the point

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8
Q

What does a displacement time graph show?

A

how distance travelled by an object from a fixed point and direction change with time

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9
Q

How is a steady speed represented on a displacement-time graph?

A

straight line with constant gradient

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10
Q

How can instantaneous velocity at a particular time be found on a curved v-t graph?

A

by drawing a tangent to the curve at the given time

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11
Q

What does a curved line on a v-t graph represent?

A

changing acceleration

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12
Q

What does a value of zero on an object’s a-t graph indicate?

A

object moving with constant velocity at given time

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13
Q

What are the conditions for an object to be in free fall?

A

It only has its weight acting on it

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14
Q

Give the properties for the acceleration of a projectile

A

acceleration is due to gravity, it is always downwards, and only affects the vertical motion of the object

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15
Q

If an object is only moving vertically, what direction is regarded as positive?

A

upwards

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16
Q

What is the acceleration for an object launched horizontally with an initial velocity U?

A

accelerates downwards at 9.81m/s/s

17
Q

What happens to the trajectory of a projectile if air resistance acts on it?

A

downward trajectory will be steeper than upward trajectory

18
Q

Define inertia

A

tendency of an object to remain in a steady state at rest, or moving in a straight line at a constant speed

19
Q

State Newton’s first law of motion

A

velocity of an object will only change if a force is acting on it

20
Q

State Newton’s second law of motion

A

acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object

21
Q

why do forces occur in pairs?

A

Newtons third law - whenever two objects interact with each other, they exert equal and opposite forces on each other

22
Q

What are the properties of a pair of forces related by Newton’s third law?

A

same size; act on separate objects; act in opposite directions; along the same line; same type

23
Q

What is the principle of conservation of momentum?

A

total momentum before collision = total momentum after collision

24
Q

What is conserved in elastic collision?

A

kinetic energy

25
Q

What is the relationship between force and momentum?

A

f = change in mv / t

26
Q

State Newtons second law in terms of momentum

A

Force acting on an object is equal to rate of change in momentum

27
Q

state the relationship between momentum and impulse

A

impulse = change in momentum (mv - mu)

28
Q

What does the area under the line of a f-t graph represent?

A

impulse of the force

29
Q

Define power

A

rate of energy transfer or rate of work done

30
Q

State the relationship between power, work done and time

A

p = change in w/t

31
Q

Define efficiency

A

measure of how much energy is wasted in a n energy transfer

32
Q

State the principle of conservation of energy

A

Energy cannot be created or destroyed, only transferred

33
Q

give the equation used to calculate the change in an object’s gravitational potential energy store

A

E = mgh

34
Q

Give the equation used to calculate the amount of energy in an object’s kinetic store

A

E = (1/2)mv^2

35
Q

Give the equation used to calculate the amount of energy in an object’s elastic potential store

A

E = (1/2)kl^2

Physics (6 decks)

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