Forces and their effects

Question 1

Describe how non contact forces interact with examples

Answer 1

• Gravitational: when there is a force between two objects with mass, the larger one has more attraction. e.g. earth and humans
• Electrostatic: Like charges repel, opposite charges attract. larger charge has greater force. e.g. static electricity
• Magnetic: Like poles repel, opposite poles attract. Stronger magnet has a stronger field. e.g. bar magnet

Question 2

Describe how contact forces interact

Answer 2

• Normal contact: force perpendicular to plane of contact

Question 3

How do two forces interact?

Answer 3

• Both forces feel an equal but opposite force
• Can be represented with arrows to show size of force and resultant force.

Question 4

contact force goes up on free body
- The reaction force always acts at the normal to the line of contact, from the point of contact
- Friction acts in the opposite direction to movement, along line of contact
- Weight always acts downwards, acting from Centre of Mass

Answer 4

just know it

Question 5

How to find direction of resultant force when vectors aren’t in straight line

Answer 5

• draw parallelogram
• Resultant force is diagonal of the parallelogram

Question 6

How do you know when a resultant force is 0

Answer 6

• All forces add up to 0
• forms a triangle when 3 forces

Question 7

How do you resolve a force?

Answer 7

• Add a horizontal and vertical component to make it into a triangle and easier to measure.

Question 8

What is a moment?

Answer 8

• Turning affect of a force

Question 9

Formula for moment?

Answer 9

Moment(Nm) = Force x distance perpendicular to direction of force.

Question 10

When does equilibrium occur in moments?

Answer 10

when clockwise moments = sum of anticlockwise moments, means that object isn’t turning.

Question 11

How do levers work?

Answer 11

Make it easier to do work, increase distance between force applied and pivot, to increase turning force making it easier to lift what’s on the other side of the pivot

Question 12

How do gears work?

Answer 12

• Circular cogs with teeth
• used to transfer rotational effect of a force from one place to another
• a small cog has a low moment
• spins a big cog with the same force
• since the cog has a higher distance to pivot, turning force is larger
• The ratio of moments is related to the ratio of teeth.

Question 13

How do you reduce unwanted energy loss in cogs?

Answer 13

• Use lubrication
• Reduces friction
• Reduces energy through heat loss