Mechanics Flashcards

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1
Q

What is meant by a scalar quantity

A

A quantity that has no direction only a magnitude

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2
Q

What is a vector quantity

A

A quantity that has a magnitude aswell as direction

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3
Q

Are the following vector or scalars:

1) Acceelration
2) Mass

A

1) vector
2) scalar

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4
Q

What is the difference between weight and mass

A

Mass is scalar, and is not dependant on the gravity acting on it.

Weight is a vector and is dependant of the gravitational field strength

w=mg

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5
Q

Define the principle of moments

A

If an object is in equilibrium the sum of the clockwise movements are equal to the sum of the anticlockwise moments

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6
Q

If the object is in equilibrium it means that:

A

the object has no resultant force (accelerating)

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7
Q

What is a Moment

A

A Turning force:

Force multiplied by perpendicular distance from the pivot to the line of action of the force

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8
Q

What is meant by a couple

A

a pair of equal and opposite coplanar forces

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9
Q

What is meant by the centre of mass

A

The point through which all the weight of an object acts

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10
Q

What is Velocity

How do you find it on a displacement time graph

A

Change in displacement / Change in time

Gradient of the tangent to the line of time you require

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11
Q

What’s the area under a velocity time and accleration time

A

velocity time - displacement

accleration time - velocity

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12
Q

Describe the relationship between air resistance and speed

A

Air Resistance is proportional to the square of the speed

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13
Q

In projectile motion what is the vertical and horizontal accleleration equal to

A

Horizontal - 0 ms^-2

Vertical acceleration = -g accelerating upwards

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14
Q

What is meant by terminal velocity

A

When weight due to gravity and air resistance acting on a falling object become balanced.

The acceleration becomes zero and the object is moving at its maximum velocity

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15
Q

What is meant by friction

A

a resistance to motion between an object and the atoms it is in contact with

Force Always Acts in the opposite direction to the motion

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16
Q

What is Newton’s third law

A

that every action force has an equal but opposite reaction force

17
Q

What is Newton’s second law/

A

F= MA
Force applied is directly proportional to both the mass and the acceleration

18
Q

What is newton’s first law

A

if the object is in equilibrium it will stay in motion or stationary until an external force acts upon it

19
Q

What is the difference between elastic and in elastic collisions

A

Elastic collision —> KE before is equal to KE After

Inelastic collision —> KE before is not equal to KE after

20
Q

Give an equation that can be used to calculate momentum

A

Mass*Velocity

21
Q

What is always conserved in collisions?

A

Momentum

22
Q

What is the rate of change of momentum

A

Force

23
Q

What is an impulse

A

Change in momentum

Force*Time = Change in momentum

24
Q

What does the area under a force time graph represent?

A

Change in momentum

25
Q

What is power?

A

The rate of which work is done.

26
Q

What is efficiency?

A

The useful power output / inputed power

27
Q

Explain the principle of conservation of energy

A

Energy can opt be created or destroyed only transferred

Total energy within a system will always remain constant

28
Q

It is given that before the collision the resultant momentum is acting to the right

For two cars of equal masses , traveling in opposite directions to each other

Describe the motion off the cars immediately after the collision if the collision is elastic.

A

Elastic Collisions conserve Total Kinetic energy

Any Collision conserves momentum

The trucks will not join and will be rebounded in opposite directions in order to conserve kinetic energy

Velocity of the car traveling originally to the left will have a higher velocity in order to conserve momentum