Chapter 9: Forces And Their Effects

Question 1

What do all non-contact forces have?

Answer 1

A field

Question 2

Non-contact forces:

Answer 2

• magnetic
• (static) electricity (electrostatic)
• weight/gravity

Question 3

Contact forces:

Answer 3

• friction
• reaction
• upthrust
• air resistance

Question 4

Newton’s 1st Law:

Answer 4

If an object is at rest or moving at a constant speed in a straight line (constant velocity), it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a (resultant) force

Question 5

Newton’s 2nd Law:

Answer 5

F = ma

Question 6

Newton’s 3rd Law:

Answer 6

Every action has an equal and opposite reaction

Question 7

With force diagrams (eg. A car with arrows showing forces), what needs to always be included?

Answer 7

Calculate resultant force, and then state direction (vector so it needs direction)

Question 8

How do you rearrange arrows in resultant force diagrams?

Answer 8

Tip-to-tail

Then resultant force starts from where the force comes from

Question 9

What is the resultant force in a resultant force diagram when you make a complete shape?

Answer 9

0

Question 10

How do you calculate resultant force in a resultant force diagram when the shape is not complete?

Answer 10

Part overhanging is the resultant force
OR
The piece joining the shape together starting from the start point is the resultant force

Question 11

If resultant force is 0N …

Answer 11

The object will be stationary or travelling at constant speed in a straight line (constant velocity)

Question 12

If resultant force is not 0N and is against the motion …

Answer 12

The object will be decelerating

Question 13

If resultant force is not 0N and is with the motion …

Answer 13

The object will be accelerating

Question 14

What does the moment of a force depend on?

Answer 14

• the size of the force

- where the force is applied

Question 15

What is a turning force called?

Answer 15

A moment

Question 16

How do you get the greatest moment?

Answer 16

• greatest force

- furthest distance from pivot

Question 17

Moment of a force is measured in …

Answer 17

Nm (Newton metres)

Question 18

Moment of a force (Nm) =

Answer 18

Force (N) x distance normal (perpendicular) to direction of the force (m)

Question 19

When a system involving rotational forces is in equilibrium …

Answer 19

The sum of clockwise moments = the sum of anti-clockwise moments

Question 20

If a larger gear is driven by a smaller gear … (low gear)

Answer 20

The large gear will rotate slowly, but will have a greater moment

Question 21

If a smaller gear is driven by a larger gear … (high gear)

Answer 21

The smaller gear will rotate quickly, but will have a smaller moment

Question 22

Describe relationship between radius and turning effect (moment) within gears

Answer 22

Directly proportional - if radius has doubled, turning effect doubles

Question 23

Look over ….

Answer 23

GEARS (watch video etc)