Mechanics

Question 1

Define a scalar quantity

Answer 1

Scalar quantitys have magnitude only. They do not have direction. E.g. speed, time

Question 2

Define a vector quantity

Answer 2

Vector quantitys have both magnitude and direction. E.g. acceleration, displacment

Question 3

How must vector be added?

Answer 3

Force arrows drawn tip to tale

Question 4

Define coplanar

Answer 4

If forces are coplanar they act in the same direction

Question 5

Define equlibrium

Answer 5

if the forces on a body are in equlibrium it means the resultant force is zero

Question 6

Give the conditions for forces to be in equlibrium

Answer 6

If coplanar forces act on an object, the object is in equlibrium if the forces form a closed shape when added tip to tail on a force vector diagram

Question 7

what is the weight (W) force?

Answer 7

Force due to gravity that acts towards the center of the earth

Question 8

What is the frictional (F) force?

Answer 8

Acts between two surfaces in contact, opporsite to the direction of motion

Question 9

What is air resistance/ drag?

Answer 9

Acts on an object moving through air due to collision of particles, in the opporsite direction to motion

Question 10

what are the normal contact/reaction (R) forces?

Answer 10

Foreces that act on an object in contact with a surface, acts perpindicular to the surface.

Question 11

What is tension (T)?

Answer 11

A force that streches an object

Question 12

What is boyancy/upthrust?

Answer 12

A force which acts upwards on an object partialy or fully submerged in a fluid

Question 13

What is the driving force (D)?

Answer 13

A force produced by and engine

Question 14

What are the rules for free body force diagrams?

Answer 14

> Draw a point in the center of mass of the body
Draw the body free from contact with any other object
Draw the forces acting on the body using vectors
Label the forces approprietly

Question 15

Give the equation for a moment

Answer 15

moment=Fd

Question 16

Define a moment

Answer 16

A mesure of the turning affect of a force. It is a vector quantity.

Question 17

Give the principal of moments

Answer 17

For a system to be in equlibrium, the sum of clockwise moments about a point must be equal to the sum of the anitclockwise momesnts (about the same point).

Question 18

What are the equations for resolving a force not perpindicular to a point?

Answer 18

M=Fxdsinθ M=Fsinθxd

Question 19

What are the moments of a couple?

Answer 19

A couple is a pair of forces of equal size which acts parallel to each other but in opporsite directions.
> the forces are coplanar
> they do not cause any resultant linear force
> cause rotational movement

Question 20

What is the equation for the moment of a couple?

Answer 20

Moment of a couple=size of obe of the force X perpindicular distance between the line of action of the force

Question 21

Define center of mass

Answer 21

The center of mass of an object is the singular point that you can consider the whole weight to act through.

Question 22

What is stability?

Answer 22

How stable an boject is depends on its center of mass and base area.
> the lower the center of mass the more stable the object
> the wider the base area the more stabe the object