• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Physics: Mechanics
 

Physics: Mechanics

on

  • 1,628 views

PowerPoint on Newton's Laws, gravity, forces, vectors, momentum, impulse and moments

PowerPoint on Newton's Laws, gravity, forces, vectors, momentum, impulse and moments

Statistics

Views

Total Views
1,628
Views on SlideShare
1,628
Embed Views
0

Actions

Likes
1
Downloads
42
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Physics: Mechanics Physics: Mechanics Presentation Transcript

    • Newton’s Laws And forces, vectors, gravity, momentum, impulse and moments
    • Newton’s First Law
      • Objects at rest remain at rest
      • Objects in motion remain in motion
      • UNTIL YOU APPLY A FORCE
    • Newton’s Second Law
      • F = ma
      • What forces are important in sports?
    • Newton’s Third Law
      • For every action there is an equal and opposite reaction.
      • But do they act on the same body?
    • Vector
      • Force is a vector - ?
      • It has a magnitude and a direction.
      • This allows forces to be cancelled out.
      • Force brings about acceleration
      • Which law relates to that?
      • Newton’s 2 nd Law
      • F=ma
    • Non-parallel forces
      • Can add vectors in different directions:
      • c 2 = a 2 + b 2 ; angle x = tan -1 a/b
      x Resultant force a b c
    • Vectors
      • Remember: the resultant force is not a new force
      • It is the sum of the 2 components
      • Use either the resultant or component in any calculation, not both!
    • Newton
      • What is a Newton?
      • Unit
      • 1N = force that accelerates 1kg mass by 1ms -2
    • weight
      • What’s the weight of 1 litre of water?
      • 1kg is the mass
      • The weight = mass x g
      • g is the gravitational field strength
      • g = 10 N kg -1
      • or 9.81 N kg -1 (more accurately)
      • Weight of 1 litre of water is 10N or 9.81N
    • Quiz
      • What is my acceleration due to weight?
      • 9.81 ms -2
      • What is your acceleration due to weight?
      • 9.81 ms -2
      • What about the marker?
      • 9.81 ms -2
      • Acceleration due to weight is always g
    • Mass
      • Amount of matter
      • Measure of inertia
      • Inertia is the resistance to acceleration
      • Mass attracts gravity
      • Gravitational force is directly proportional to mass
      • Note: Gravitational force is inversely proportional to distance 2 between 2 points
    • Quiz
      • As one moves away from the centre of the earth, his/her weight decreases.
      • At 3000m, g = 9.8009 N kg -1
      • What if we throw shot put at 3000m?
      • What if we run marathon at 3000m?
      • At 3000m, oxygen pressure is reduced by more than 10%
      • Always consider other factors!
    • Impulse
      • Momentum = mass x velocity
      • Since F = ma and a = ∆ v / t , F = m ∆ v / t
      • Therefore F t = m ∆v, or
      • Impulse = change of momentum
      • The larger the impulse, the greater is the change in velocity.
      • Application?
    • Impulse
      • Hence, to increase velocity, we either increase F or t (time of contact).
      • Remember, F = m ∆ v / t
      • To reduce impact, encourage soft landing
      • Use cushioning, bend joints, etc
    • Conservation of energy
      • Energy is always conserved
      • Regardless of whether you can observe
      • Mechanical energy is not always conserved
      • Mechanical energy is only conserved in a closed system
      • Initial (total kinetic + potential energy) = final (total kinetic + potential energy)
    • Conservation of momentum
      • Momentum is conserved when there is no external forces
      • E.g. snooker, assuming no friction
      • Application?
      • Momentum can be transferred in a collision
      • Application?
    • Conservation of Momentum If m 1 = m 2 , then v 1 = v 2 http://www.phys.washington.edu/~young
    • Moments
      • Turning effect of a force
      • Moment = force x perpendicular distance
      • Also called torque