topic 2

• What is a vector quantity?

  a quantity that has both magnitude and direction
• What is a scalar quantity?

  A quantity that has only magnitude
• What are examples of vectors?

  displacement, velocity, acceleration, force
• What are examples of scalars?


  distance, speed, mass
• What is the equation for velocity?

  v=d/t
• What is acceleration?


  The rate at which velocity changes
• What is the formula for acceleration? (basic)

  a = (v-u)/t
• What is the formula for acceleration? (advanced)

  v^2-u^2 = 2 x a x X (X = distance)
• how do you find the distance in velocity time graphs?

  the area under the graph
• What is the gradient on a velocity-time graph?

  the acceleration
• What is Newton's first law?

  An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a resultant force.
• What is Newton's second law?

  Force = mass x acceleration
• What is inertia?


  The tendency of an object to resist a change in motion
• What is Newton's thrid law?

  For every action there is an equal and opposite reaction
• How can you investigate the motion of a trolley on a ramp?

  1) set up the light gate (measure speed which it goes through) and the trolley with a card

  2) adjust the height of the ramp so that the trolley just starts to roll. Therefore, the hanging mass will be the cause of it rolling, so gravity

  3) the weight og the hook and masses attacted to it will provide the accelerating force, euqal to mass x acceleration.

  4) calculate acceleration using the initial and final speed from the light gates, as well as the time taken

  5) repeat experiment, changin either:

  - the mass of the trolley by adding masses to the trolley each time

  - to investigate the effect of the force on acceleration, transfer weights from the hook to the trolley (so the weight of the whole system stays the same). This will change the mass due to gravity
• What is weight?


  the force of gravity on an object
• What are the units for weight?

  Newtons (N)
• What is the formula for weight?

  Mass x gravitational field strength
• What are the units for gravitational field strength?


  N/kg
• What is the formula for momentum?

  p=mv
• What are the units for momentum?

  kg m/s
• What is momentum?


  A property that all moving objects having, kind of like a driving force
• What is conservation of momentum?


  In a closed system, the total momentum before an event is the same as after the event
• What is the formula for force (involving momentum)


  F = change in momentum/ time
• How can you measure reaction time?

  Ruler drop test

  1)hold ruler between thumb and forefinger, zero end is level

  2)let go without warning

  3)person catches as quick as they can, reaction time is measured from the number where it's caught, from top of thumb

  4)higher the number the slower reaction time

  5)repeat several times, calculate mean

  6)then person being tested should drink caffeinated drink and repeat after 10 minutes

  7)CONTROL - same person, same hand, dropped from same height.
• What is a more accurate method to measure reaction time?

  Making someone click a mouse when a colour changes on a screen
• What is thinking distance?

  How far the car travels during the driver's reaction time
• What is braking distance?

  The distance your car travels after you apply the brakes
• What is the formula for stopping distance?

  Stopping distance = thinking distance + braking distance
• What factors affect thinking time?

  - your speed - the faster you go, the further you travel during your reaction time

  - reaction time - the longer it takes you to react, the longer your thinking distance
• What factors affect braking distance?

  -speed

  -mass of the vehicle

  -quality of the breaks

  -road surface
• Why are large deccelerations dangerous?

  - they require a large force

  - this force can be lowered by slowing down the object oer a longer time

  - safety features like airbags and the slight stretch on seatbelts increase collision times in order to reduce the force on the person in the car
• What is the rule concerning kinetic energy and braking?

  Energy in the car's kinetic energy store = work done by the brakes

  
  

  1/2 x m x v^2 = F x d
• what factors affect the magnitude of a centripetal force?

  velocity of object (increase causes increase)

  mass of object (increase causes increase)

  distance of object from centre of its orbit(shorter distance causes increase)
• In the case of an atom, what word describes the forces which keep these particles moving in circular paths around the nucleus?

  electrostatic
• what provides the centrapetal force needed to keep a satellite in its orbit around earth?

  gravitational pull
• why does the kinetic energy of a satellite orbiting earth remain constant?

  because its speed and mass are both constant