1991 past paper

[S.McGrath]

theres a question in it that says
A tennis player hits a ball at a height of 2.4m. The ball has an initial horizontal
velocity. The ball just passes over the net that is 0.6m high and 6m away from her.
(Neglect air resistance)

(a) Calculate the time required for the ball to reach the net.
(b) What was the speed of the ball as it left the racquet?


i dont know how to work it out, i know to split it into horizontal and vertical components, but i dont know wat to put for U & V for them

[Admin]

a) Work in the vertical to find t, u = 0 m/s, v = ?, a = 9.8 m/s^2, s = (2.4 - 0.6), t = ?;
S = ut + 1/2 at^2; so 1.8 = 0 + 4.9t^2; t^2 = 1.8/4.9 = 0.367s; t = 0.6 s

b) Work in the horizontal s = vt, s = 6 m, t = 0.6 s,v = ? ; v = 6 / 0.6 = 10 m/s

[S.McGrath]

haha i had that but i didnt think i could work part a out without 2 variables

[S.McGrath]

sir, this is an unfair amount of homework

[Admin]

No, 2 hours in school and 2 hours HW over Thurs night and weekend in not too much. Get used to it because it is the new normal until the exams.

[S.McGrath]

haaaaarsh

[Admin]

Maybe but I believe it will improve your grades remember in an exam time is also your enemy so if you can get faster due to workload then the exam gets easier as you can finish it quicker. "Train hard fight easy" your fight is the higher in May.

[S.McGrath]

i dont get question 7b) in the 1992 past paper, paper 2. i dont remember doing it

[Admin]

Use the equation Q = It find Q when I = 15mA and t = 1 so Q = 15 mC, use the charge of an electron 1.6 x10^-19 C to find how many electrons make 15mC.