Topic 8 Forces in Balance

Question 2

What is a scalar quantity?

Answer 2

A quantity that has magnitude only (no direction).

Question 3

What is a vector quantity?

Answer 3

A quantity that has both magnitude and direction.

Question 4

Give three examples of scalar quantities.

Answer 4

Speed, distance, mass.

Question 5

Give three examples of vector quantities.

Answer 5

Velocity, force, displacement.

Question 6

What is force measured in?

Answer 6

Newtons (N).

Question 7

What is displacement?

Answer 7

The straight-line distance and direction from a starting point.

Question 8

How is a vector represented in diagrams?

Answer 8

As an arrow showing direction and magnitude.

Question 9

What is the difference between distance and displacement?

Answer 9

Distance is scalar (total travelled), displacement is vector (direct line).

Question 10

What happens if forces on an object are balanced?

Answer 10

The object remains stationary or continues moving at constant velocity.

Question 11

What happens if forces on an object are unbalanced?

Answer 11

The object accelerates in the direction of the resultant force.

Question 12

What is the resultant force?

Answer 12

A single force that has the same effect as all the original forces acting together.

Question 13

How do you find the resultant force when forces act in the same direction?

Answer 13

Add them together.

Question 14

How do you find the resultant force when forces act in opposite directions?

Answer 14

Subtract the smaller force from the larger.

Question 15

What is meant by equilibrium?

Answer 15

When forces are balanced and the object does not accelerate.

Question 16

What is the moment of a force?

Answer 16

The turning effect of a force around a pivot.

Question 17

What is the formula for moment?

Answer 17

Moment = Force × Distance (from pivot).

Question 18

What is the unit of a moment?

Answer 18

Newton metres (Nm).

Question 19

What is a pivot?

Answer 19

The point about which something rotates.

Question 20

What factors affect the size of a moment?

Answer 20

The force applied and the perpendicular distance to the pivot.

Question 21

How can you increase the moment of a force?

Answer 21

Increase the force or the distance from the pivot.

Question 22

What does the principle of moments state?

Answer 22

For an object in equilibrium, clockwise moments = anticlockwise moments.

Question 23

What is meant by a lever?

Answer 23

A rigid bar that pivots around a point to multiply force.

Question 24

How do levers make tasks easier?

Answer 24

They increase the distance from the pivot, reducing the force needed.

Question 25

What is a gear?

Answer 25

A wheel with teeth that transmits rotational force.

Question 26

How can gears change force?

Answer 26

Larger gears create greater moments, smaller gears turn faster with less force.

Question 27

How does a gear system with a small gear driving a larger gear behave?

Answer 27

Larger gear turns slower but with more force.

Question 28

How does a gear system with a large gear driving a smaller gear behave?

Answer 28

Smaller gear turns faster but with less force.

Question 29

What is a free-body diagram?

Answer 29

A diagram showing all the forces acting on an object.

Question 30

How are forces represented on a free-body diagram?

Answer 30

As arrows; size shows magnitude, direction shows the force direction.

Question 31

What does resolving a force mean?

Answer 31

Splitting a force into horizontal and vertical components.

Question 32

What is a resultant force in two dimensions?

Answer 32

The single force combining the effects of horizontal and vertical forces.

Question 33

How do you calculate the resultant of two perpendicular forces?

Answer 33

Use Pythagoras' theorem: √(horizontal² + vertical²).

Question 34

What is stability?

Answer 34

The ability of an object to return to its original position after being tilted.

Question 35

How can you make an object more stable?

Answer 35

Lower its centre of mass or widen its base.

Question 36

What is the centre of mass?

Answer 36

The point at which the entire mass of an object can be thought to act.

Question 37

Where is the centre of mass for a symmetrical object?

Answer 37

At its centre.

Question 38

How can you find the centre of mass of an irregular shape?

Answer 38

Hang it freely from two points and draw vertical lines; the intersection is the centre.

Question 39

What happens if the line of action of the weight is outside the base?

Answer 39

The object will topple.

Question 40

How does increasing the base area affect stability?

Answer 40

It increases stability by making it harder to topple.

Question 41

How does lowering the centre of mass affect stability?

Answer 41

It increases stability.

Question 42

Why do wider vehicles have a lower risk of toppling?

Answer 42

They have a wider base and a lower centre of mass.