Mechanics

Question 1

Scalar Quantity?

Answer 1

A quantity with only a magnitude and no direction. Examples include speed, mass and temperature

Question 2

Vector Quantity?

Answer 2

A quantity with a magnitude and direction. Examples include velocity, force and acceleration

Question 3

Free Body Diagram?

Answer 3

Show a single body on its own and include all the forces acting on the body but not the forces it exerts on the rest of the world

Question 4

Equilibrium?

Answer 4

All forces acting will be balanced and cancel each other from being equal and opposite, meaning there is no resultant force. Equilibrium can be at rest or an object moving with a constant velocity

Question 5

Mass?

Answer 5

The amount of matter in an object

Question 6

Inertia?

Answer 6

The greater an objects mass the greater its resistance to change velocity

Question 7

Moment?

Answer 7

The turning effect of a force around a turning point. The moment is dependant on the size of the applied force and how far it is from the turning point

Question 8

Principle of moments?

Answer 8

For a body to be in equilibrium the sum of clockwise moments about any point equals the sum of the anti-clockwise moments about the same point and if they aren’t balance the object will turn

Question 9

Levers?

Answer 9

Levers increase the distance from the pivot a force is applied, meaning less force is needed to generate the same moment from the effort force acting against a load force from a rigid object rotating around a pivot

Question 10

Couple?

Answer 10

A pair of forces equal in size and act parallel to each other but in opposite directions. A couple doesn’t cause any linear force but produces a moment dependent on size of the forces and distances between them

Question 11

Centre of mass?

Answer 11

A single point where the whole weight of an object acts through whatever its orientation

Question 12

Experimentally finding centre of mass?

Answer 12

Hang the object freely from a point. Draw a vertical line downwards from the suspension point using a plumb bob as a marker. Hang from a different point and draw another line. The intersection point identifies the centre of mass

Question 13

Toppling objects?

Answer 13

If an object’s weight from the centre of mass is outside its base area it will topple over since a resultant moment occurs which produces a turning force causing it to fall over. An object is more stable with a wider base area and lower centre of mass

Question 14

Forces on suppourts?

Answer 14

The closer the objects centre of mass is to a support the stronger the force on the support

Question 15

Velocity?

Answer 15

Rate of change of an objects displacement

Question 16

Instantaneous Velocity?

Answer 16

The velocity of an object at a particular moment in time and on a displacement time graph is found by drawing a tangent at this particular moment in time

Question 17

Advantages of data loggers?

Answer 17

The data is more accurate as it doesn’t allow for human error like reaction time, the sampling rate is much higher, the data is displayed in real time

Question 18

Acceleration-time graphs?

Answer 18

Positive value of acceleration indicate the object is speeding up and accelerating however if they are negative they indicate it is slowing down so is decelerating

Question 19

Newton 1st Law?

Answer 19

The velocity of an object will not change unless a resultant force acts on it. This means a body will be stationary or move in a straight line at a constant speed with no resultant force

Question 20

Newtons Second Law?

Answer 20

The acceleration of an object is proportional to the resultant force acting on it

Question 21

Newtons 3rd Law?

Answer 21

If an object exerts a force on another object, that object will exert an equal but opposite force back on the other object

Question 22

Freefall?

Answer 22

The motion of an object undergoing an acceleration due to gravity. The only force acting on the object is its own weight

Question 23

Determining “g” using a free fall method?

Answer 23

Have a circuit featuring a timer, switch, trap door and electromagnet. Measure height from bottom of ball bearing to trap door. Flick the switch and time timer will start and disconnect the electromagnet releasing the ball bearing. When it passes through the trap door it breaks the circuit which produces a time value. Repeat 3 times at this height and find an average time. Repeat method but for different heights

Question 24

Friction?

Answer 24

A force which opposes motion. There are two types: contact friction and fluid friction. Contact friction happens between solid surface and fluid friction is fluid resistance in a liquid or gas.

Question 25

Factors affecting fluid friction?

Answer 25

Viscosity of fluid. Force increases as speed increases. Force depends on the shape of an object moving through it so the larger the area against the fluid the greater the resistance force

Question 26

Lift?

Answer 26

An upwards force on an object moving through a liquid and occurs when an object causes the fluid flowing over it to change direction. This force is perpendicular to the direction the fluid is flowing

Question 27

Terminal speed?

Answer 27

Otherwise terminal velocity happens when frictional forces equal the driving force

Question 28

Principle of liner momentum?

Answer 28

The total linear momentum of two objects before they collide equals the total linear momentum after the collision

Question 29

Elastic Collision?

Answer 29

A collision where momentum and kinetic energy is conserved

Question 30

Inelastic Collision?

Answer 30

A collision when momentum is conserved but kinetic energy of a collision is not conserved

Question 31

Impulse?

Answer 31

Defined as the product of force and time. The impulse on a body is equal to the change in momentum of that body

Question 32

Joule?

Answer 32

The work done when a force of 1 newton moves an object through a distance of 1 meter

Question 33

Power?

Answer 33

The rate of doing work, otherwise the amount of energy transferred per second

Question 34

Watt?

Answer 34

Has the symbol "W" and is defined as the rate of energy transfer equal to 1 joule per second