Forces (yr10)

• what does a vector quantity have

  magnitude and direction
• what does a scalar quantity have

  magnitude
• name 4 examples of vector quantities

  1 displacement

  2 velocity

  3 force

  4 weight
• name 4 examples of scalar quantities

  1 distance

  2 speed

  3 time

  4 mass
• what is the equation for displacement

  $s =$$vt$
• what is the equation for acceleration

  a = (delta) v/ t
• what is the equation for velocity

  v = (delta) s/ t
• what is the equation for gravitational potential

  GPE = mgh
• what is the equation for kinetic energy

  $KE =$$1/2 mv^2$
• what can you interpret from the equation: $KE =$$1/2 m v^2$


  1 that mass and kinetic energy have a direct proportion

  2 that velocity and kinetic energy have an exponential proportion
• what is an equation of motion 


  $v^2-u^2=$$2as$
• what is a contact force 


  a force that only acts when objects are in contact
• what is a non-contact force


  a force produced because an object is in a field (they do not have to be in contact)
• give 2 examples of non-contact forces 


  1 electrostatic force

  2 gravity
• give 2 examples of contact forces


  1 friction

  2 upthrust
• what 2 things must be identified when creating a free body diagram


  1 the non-contact forces

  2 the contact pairs
• what is a resultant force 


  the force when two or more forces are added together as vectors
• what is newton's first law 


  objects will remain at rest, or move with a constant velocity unless acted upon by another force
• what is inertia 


  the tendency of an object to continue in its current state
• what is newton's second law 


  $\Sigma F\ =$$\ ma$
• what 2 things can you interpret from the equation F=ma 


  1 the acceleration of an object is proportional to the resultant force on the object

  2 the acceleration is inversely proportional to the mass of the object
• what is inertial mass 


  the ratio of force over acceleration
• what is newton's third law 


  when two objects interact, they exert equal and opposite forces on eachother
• what is terminal velocity


  the velocity a moving object achieves when the resultant force is zero
• explain the motion of a skydiver 


  • when you jump out of the plane you accelerate so the force of the air increases
  • eventually the force of the air equals the force of the Earth on you meaning your motion no longer changes (reached terminal velocity)
  • when a parachute is opened it increases the force of the air to reduce your velocity
• what is momentum 


  $p\ =$$mv$
• what is the law of the conservation of momentum 


  total momentum before = total momentum after

  $p1+$$p2\ =$$\ p1+$$p2$
• what is a closed system 


  when there are no outside factors to consider
• what happens in elastic collision 


  when objects collide they will move in opposite directions and no energy is transferred
• what happens in inelastic collisions 


  when objects collide they move in the same direction, together (become one mass) and some energy is transferred
• how can you rewrite F=ma for momentum 


  $F=$$\ \frac{\Delta mv}{t}$
• what can you interpret from the equation $F=$$\frac{\Delta mv}{t}$


  that force and time are inversely related
• what is work 


  W = Fs
• what is the unit for work 


  Joules (J)
• what is power 


  $P=$$\frac{W}{t}$
• what is the unit for power 


  Watts (W)
• What 3 ways can an object change shape

  compression

  tension

  bending
• what is compression 


  when the two forces (weight and reaction force) act towards each other
• what is tension


  when the two forces (weight and tension) act away from each other
• what is bending 


  when the two forces (weight and reaction force) act toward each other at different point on the object