3. Rectilinear Motion & Equations for motion for uniform acceleration Scalar Velocity SpeedVector AccelerationDistance Displacement Average Speed Average Velocity Instantaneous Velocity What do these terms mean? If you are unsure look them up in one of your books! Try to group them together in to Scalars and Vectors!

4. You should be familiar with the following: = initial velocity uvtsauvtsa = final velocity = time = displacement (sometimes s) = acceleration Equations for motion for uniform acceleration The following equations can be derived but you do not need to know how.

5. v = u + at or a = (v-u)/t s = ut + 1 / 2 at 2 v 2 = u 2 +2as s = (u+v)t/2

6. A 5p coin is thrown downwards off the top of the Eiffel Tower at 2ms –1. If it takes 7.6s to hit the ground after accelerating constantly at 9.81ms –2, from what height was it dropped? (Does this seem reasonable??) s = ut + ½at 2 s = 2*7.6 + ½*9.81*(7.6 2 ) s = 15.2 + 283.3 s = 299m

7. Voyager was travelling at 15ms -1 when the reverse thrusters were applied. The shuttle eventually reversed after 5s and travelled in the opposite direction with a velocity of 5ms -1. What is it’s average acceleration? a = (v-u)/t a = (-5 – 15)/5 a = -20/5 a = -4 ms -2

8. Some specially trained pilots can withstand accelerations of up to 11g. Schumacher experiences approximately 3g in his F1 car. What would be the shortest distance needed to get to the speed of sound if the pilot could pull 11g from a standing start? Assume g = 10 ms -2 and speed of sound is 330 ms -1. v 2 = u 2 +2as 330 2 = 2*(11*10)*s s = 495m

10.  PAG 1 1.1  Comparing methods of determining ‘g’

11. Measuring acceleration due to gravity

12. Theory Using s = ut + 1 / 2 at 2 we can derive h = 1 / 2 gt 2 This of the form y = mx +c h on the x axis and t 2 on the y axis gradient 1 / 2 g such that if we plot h on the x axis and t 2 on the y axis we should obtain a straight line of gradient 1 / 2 g which passes through the origin. Method: Obtain at least 8 sets of results for h, the distance the ball fell through and t, the time taken over as wide a range as possible.

13. h - the distance through which the ball fell (with a metre rule) t - the time taken for the fall (with a centisecond counter). Measurements: Determination of g: plot a graph of s vs t 2 determine the gradient use g = 2 x gradient to evaluate g in ms -2. this comes from the theory section (gradient = 1/2g)

14. Sources of error - how to reduce this: · parallax error when reading h - bob down so that you are at eye level when taking measurements · random fluctuations - take several readings at each height and look at the spread of results. This is only one method could you come up with another using the light gates?

15. Square card as shown dropped through the gates As dimensions are known you can get the acceleration from the correct calculation. Known length Known thickness Light gate measure time for each side of the card to pass through and therefore the velocity of each side and therefore the acceleration of the card!

17.  Vehicles can't just 'stop dead' - they are big and heavy, and if someone steps in front of them the driver may have no chance of stopping in time.

18.  Stopping distance depends on the speed of the car.  That is why we have speed limits - the more likely it is for a driver to have to stop, the lower the speed limit. A road with houses on it normally has a 30mph limit but a motorway has a limit of 70mph because there should be no one trying to cross it.

19.  Stopping distances are spilt into two sections:  during the time it takes the driver to put his/her foot on the brake and push it to the floor (the reaction time) the car travels the thinking distance and  during the time it takes for the car to stop once braking has started the car travels the braking distance.

20.  Braking distance is affected by:  The car (worn brakes, extra weight, bald tyres etc)  The road (poor surface, spilt oil etc)  The weather (wet, icy - anything that reduces friction)

21.  Thinking distance is affected by:  The driver's reaction time.  Your reaction time can be affected by:  distractions in the car,  distractions outside the car (not just distractions - sunlight reflected into eyes can affect the time interval between the braking occurance happening and the driver reacting to it),  alcohol,  medication,  age - your thinking processes slow as you approach old oge.

23.  Braking distance is the area under the graph of the velocity/time graph showing the deceleration of the vehicle against time. If you double the velocity at which you apply the brakes you will double the time it takes to come to a standstill.... but the distance you travel in that time will go up by a factor of four!  So, the faster the vehicle is travelling the greater the actual braking distance is compared to the thinking distance by the square of the factor that increased the speed - it is a squared relationship between speed and distance..

24.  Thinking distance is the time the vehicle travels in the reaction time - the time it takes to realise you have to stop! Let us say the reaction time (time between you realising you need to stop and you actually hitting the brake) is 0.5s.  At 20 m/s (about 44 mph) the car will travel about six metres before the brakes are applied.  At 40 m/s it would be twice as far... the thinking distance is directly proportional to speed.

25.  Factsheet 13  Motion Support  Calculation Sheet 3  Calculation Sheet 3.5  Practical 3.3 – Acceleration  Practical 3.7 – Free Fall and ‘g’  Application – Equations of Motion