Unit 3

• Balanced forces are equal in strength and do not change an object's motion.
• Unbalanced forces are unequal in strength and cause change in an object's motion.
• Speed = distance / time
• Distance=speed x time
• Time = Distance/speed
• Units of speed: mph, km/h, m/s
• Moment (Nm) = Force(N) x Distance(m)
• Force = Moment/Distance
• Pressure = force/area
• Distance= Moment/Force
• Marcus weighs 600N and sits at a distance of 2m from the pivot of a seesaw. Arun weighs 800N. Where should Arun sit to make sure the seesaw is balanced?

  Marcus's moment = 600 x 2

  = 1200 Nm

  Arun's distance from pivot= 1200/800

  = 1.5m
• The total weight of a bicycle and rider is 1000N.

  The bicycle has 2 tyres in contact with the ground. The weight is supported equally on both tyres.

  The area of each tyre in contact with the ground is 5cm².

  What is the pressure that each tyre exerts on the ground?

  Weight of one tyre=1000/2

  = 500N

  Pressure=force/area

  =500/5

  =100N/cm²
• Unit for pressure:N/cm²
• Unit for moment: Nm
• Pressure increases with depth.
• Pressure increases with depth

  A) Pressure increases with depth

  B) Weakest jet

  C) Strongest jet

  
• Atmospheric pressure decreases as altitude increases
• Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
• Factors of diffusion:

  A) Higher temperature

  B) Larger surface

  C) Higher Gradient

  D) Smaller particles

  E) Solid → Slowest

  F) Liquid → Faster

  G) Gas → Fastest