Moments

Question 1

What is weight?

Answer 1

The downward force a mass has due to gravity

Question 2

What is weight measured in?

Answer 2

Newtons

Question 3

What is mass?

Answer 3

The amount of matter an object is made of.

Question 4

What is mass measured in?

Answer 4

Grams (g) or kilograms (kg)

Question 5

What is w = m x g

Answer 5

Weight = mass x gravitational field strength

Question 6

What is a pivot?

Answer 6

The point of which a lever can rotate around when a moment is present

Question 7

What is a lever?

Answer 7

A rigid body which revolves around the pivot

Question 8

What is a moment?

Answer 8

The turning effect of a force

Question 9

What is the equation to calculate moments?

Answer 9

Moment = force x perpendicular distance

Question 10

What is a moment measured in?

Answer 10

Newton meters (Nm)

Question 11

What is perpendicular distance measured in?

Answer 11

Meters (m) or centimetres (cm)

Question 12

What is effort?

Answer 12

The force exerted on the lever

Question 13

What is load?

Answer 13

The force that is being moved

Question 14

define elastic limit

Answer 14

The point beyond which materials that are elastic no longer obey hooke’s law

Question 15

Define plastic deformation

Answer 15

The permanent deformation when an unloaded material that has previously been stretched or squashed doesn’t return to its original shape

Question 16

Define contact force

Answer 16

Any force that can only be exerted when objects are touching

Question 17

Define non-contact force

Answer 17

Any force that can be exerted without objects touching

Question 18

What is Center of mass?

Answer 18

The point from which the weight of an object appears to act from

Question 19

What is hooke’s law?

Answer 19

That for a spring,force is directly proportional to extension up until the elastic limit

Question 20

What is directly proportional?

Answer 20

When one variable increases, the rate that the other increases by remains constant

Question 21

What is extension?

Answer 21

Extension of elastic material = original length - new ( stretched length)

Question 22

What is the equation for Hooke’s law?

Answer 22

F = k x e ( force = spring constant x extension)

Question 23

What is force measured in?

Answer 23

Newtons N

Question 24

What is elastic deformation?

Answer 24

The deformation whereby an elastic material that has been stretched returns to its original Shape afterwards

Question 25

How do you find the center of Mass on a regular object?

Answer 25

Find two lines of symmetry and the Center where the two lines meet is the Center of mass.

Question 26

How do you find the Center of mass on an irregular object?

Answer 26

Punch a hole in 3 places at random then hang a string from them one at a time and attach a plumb line from each one and then draw a line whilst holding the plumb line in place. Do this for all the holes and then find the place where are the lines meet and that will be the center of mass

Question 27

Is elastic deformation permanent or temporary?

Answer 27

Temporary

Question 28

Is plastic deformation permanent or temporary?

Answer 28

Permanent

Question 29

On a deformation graph, what axis are the force and extension on?

Answer 29

Force on y axis
Extension on x axis

Question 30

Does elastic deformation obey hooke’s law?

Answer 30

Yes, as both force applied to elastic material and extension are directly proportional.

Question 31

Does plastic deformation obey hooke’s law?

Answer 31

No, as the elastic material has passed it’s elastic limit, so when a force is applied, the object will stretch, but not return to its original shape.

Question 32

What is the yielding point?

Answer 32

The points that indicates the end of elastic behaviour in an object and the start of plastic behaviour

Question 33

Something is in equilibrium when….

Answer 33

Total Anti-clockwise moment = total clockwise moment

Question 34

Why would a bus with the centre of mass outside its base topple in comparison to a bus with the centre of mass in its base?

Answer 34

The bus with the centre of mass outside its base would topple over as the weight creates a destabilising anti-clockwise moment about the centre of mass so it falls. In the bus with the centre of mass inside its base, the weight of the bus creates a stabilising clockwise moment about the centre of mass so it stays upright.

Question 35

How is it beneficial for the load to be closer to the pivot?

Answer 35

The weight of the load acts from the CoM of the load, creating anti-clockwise moment about pivot. Closer the load to pivot, the smaller the moment. In order for load to be lifted, the boulder’s moment must be equal to the effort to lift the load. So, smaller moment from weight of load = smaller clockwise moment needed to lift it. Therefore, moment and so effort could be reduced to lift the load by moving the load closer to pivot or by increasing the distance effort is applied from.