mechanics-scalars,vectors,moments

Question 1

What is a scalar quantity ?

Answer 1

A quantity with only magnitude.

Question 2

what is a vector quantity ?

Answer 2

A quantity with magnitude and direction.

Question 3

Give 3 examples of scalar quantities.

Answer 3

speed
temperature
distance
pressure
energy
power
etc.

Question 4

Give 3 examples of vector quantities.

Answer 4

weight
displacement
momentum
acceleration
force
etc.

Question 5

What is the resultant force of a box 5N right and 3N left ?

Answer 5

2N right

Question 6

How would you find the resultant force of a object with perpendicular forces (right angles) ?

Answer 6

Using Pythagoras or scale drawing.

Question 7

How do you find components of a force ?

Answer 7

Use Pythagoras or trigonometry depending on the variables given.

Question 8

What does it mean when a system is in equilibrium ?

Answer 8

The resultant force is 0 and the resultant moment is 0 so the system is either stationary or at a constant velocity.

Question 9

what are coplanar forces ?

Answer 9

forces that act along the same plane.

Question 10

For a object in equillibrium on a inclined plane what is the friction equal to ?

Answer 10

The parallel component of the weight

Question 11

For a object on a inclined plane what is the normal contact equal to ?

Answer 11

The perpendicular component of the weight.

Question 12

For a object on a inclined plane what is the angle between the weight and the perpendicular component of the weight equal to ?

Answer 12

The angle of the slope.

Question 13

For a object on a inclined plane what part of a triangle is the weight ?

Answer 13

Hypotenuse.

Question 14

How do you work out the parallel component of the weight for a object on a slope ?

Answer 14

Wsinθ.

Question 15

How do you find the perpendicular component of the weight for a object on a slope ?

Answer 15

wcosθ.

Question 16

List 3 types of a force e.g. weight

Answer 16

weight
air resistance
thrust

Question 17

What is the difference between mass and weight ?

Answer 17

Weight is the force exerted by gravity the mass is a measure of the amount of material.

Question 18

What is the centre of mass ?

Answer 18

Point at which gravity acts upon.

Question 19

When will a object start to topple ?

Answer 19

When its centre of mass falls outside its base.

Question 20

What is a moment ?

Answer 20

Force multiplied by perpendicular distance.

Question 21

What is the unit for a moment ?

Answer 21

Newton metre (NM).

Question 22

If the distance=1m and Force=5 what is the moment ?

Answer 22

5NM.

Question 23

How do you find the moment of a force that isn’t perpendicular ?

Answer 23

Find perpendicular force or distance.

Question 24

What is the principle of moments ?

Answer 24

For a system in equilibrium the clockwise moments=anti-clockwise moments about any point

Question 25

If a object is uniform where is its centre of mass ?

Answer 25

Its physical centre.

Question 26

For a double pivot what is the moments about 1 pivot equal to ?

Answer 26

The normal contact of the other pivot.

Question 27

What is a couple ?

Answer 27

Two opposite and equal coplanar forces that are along the same line of action.