Physics Paper 2, MAy/June. 2013  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main

General Comments

Question 1

A projectile is released with a speed u at an angle   to the horizontal.  With the aid of a  diagram, show that the time of flight is equal to  , where g is the acceleration of free fall.






This question was very popular among the candidates and the performance was low.  Many responding candidates drew and got the shape of the graph (trajectory) however, majority failed to label the axes of the graph and  and only few indicated the initial speed u on the graph.  Some candidates also failed to realize that at the maximum height, only the vertical motion  vy  =  0.

    The expected answer is

  1.                                                                                           Both axes correctly distinguished    

Correct shape with u and  correctly shown           


                Vertical (component of) velocity  =  u sin
If time taken to reach a height is t then,
   v = u sin  - gt                                                                                                      
 At maximum height v = 0
    0  = u sin   -  gt                                                                                             
                                        t =  u sin                                                                                                     
             but the projectile takes the same time to do the rest of the flight (ie trajectory is    symmetrical)
                         Time of flight, T  =  2t  =  2usin

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