Mechanics

Question 1

What is a moment ?

Answer 1

It is the turning effect of a force. The force multiplies by the perpendicular distance between the line of action of the force and the pivot

Question 2

What does the principle of moments state ?

Answer 2

For an object in equilibrium the sum of clockwise moments is equal to the sum of the anticlockwise moments about the same point

Question 3

What is a couple ?

Answer 3

A pair of force of equal size which acts parallel to each other but in opposite directions. They produce a turning force called moment of a couple / torque

Question 4

How do you calculate the torque ?

Answer 4

The force multiplied by the perpendicular distance between the two forces

Question 5

What is the centre of mass ?

Answer 5

The point where the entire mass of an object is assumed to be concentrated

Question 6

What is the centre of gravity ?

Answer 6

The point at which all the weight is assumed to be acting

Question 7

How can you find the centre of mass of irregular objects ?

Answer 7

The intersection of the lines of symmetry

Question 8

How to you find the centre of mass of an irregular object ?

Answer 8

If the object is suspended and release the centre of mass would be directly below the point of suspension

Question 9

When is an object said to be stable ?

Answer 9

If it returns to its original position when disturbed.

Question 10

What are the factors of stability ?

Answer 10

The width of the base - the wider the width the more stable you are
The lower the centre of mass - the more stable the object is

Question 11

How does terminal velocity occur ?

Answer 11

• when an object is dropped its only component making it accelerate is the weight . Over time the air resistance increases as the speed increases until it is equal to the weight the object has now resultant force acting on it reaches terminal velocity.

Question 12

What is Newton’s first law ?

Answer 12

An object remains at constant motion or rest unless acted upon by a resultant force which causes the object to accelerate

Question 13

What is inertia ?

Answer 13

The tendency of a body to resist any change in its motion (speed or direction )

Question 14

What does Newton’s second law state ?

Answer 14

If an unbalanced force acts upon an object then the object will accelerate in the direction of the resultant force and is inversely proportional to the mass of the object

Question 15

What does Newton’s third law state ?

Answer 15

If object a exerts a force on object b then object b must exert an equal and opposite force back on the object a