Chapter 6

Question 1

Difference between a vector and a scalar?

Answer 1

Vector: magnitude and direction
Scalar: Just magnitude

Question 2

What are the 2 ways to find a resultant force?

Answer 2

• Scale diagram
• Pythagoras and Trigonometry

Question 3

If forces are balanced what will the resultant force be?

Answer 3

Zero

Question 4

If the resultant force is 0 what two things could this mean?

Answer 4

The object could be stationary or moving at a constant velocity

Question 5

What is a moment (definition)?

Answer 5

A moment is the turning effect of a force acting along a line perpendicular to a pivot

Question 6

What is the equation for a moment?

Answer 6

Moment = Force x Perpendicular distance to a pivot

Question 7

What is a moment measured in?

Answer 7

kgms^-2
Same as Joules

Question 8

What is the principle of moments?

Answer 8

For a system to be at equilibrium, the sum of the clockwise moments equals the sum of the anticlockwise moments.

Question 9

When an object at equilibrium is supported at one point only, what is the support force on the object equal to?

Answer 9

The support force on the object is equal and opposite to the downward force acting on an object.
W1d1 = W2d2

Question 10

What is the definition of centre of mass?

Answer 10

The centre of mass of a body is the point through which a single force on the body has no turning effect.

Question 11

What are the two centre of mass tests?

Answer 11

1) Balance a ruler at its centre, if the rule is uniform then the centre of mass will be exactly in the centre.
2) Suspend some card from a clamp stand with a plumb line hanging down by it and trace the line with pencil

Question 12

What is a couple?

Answer 12

A couple is a pair of equal and opposite forces acting on a body but not along the same line.