another projectile motion question (2 Viewers)

[jemsta]

this might sound easy but i dont seem to get the answer. maybe my working out is wrong anyways heres the question.
1)a body is projected with an initial velocity of 45m/s and reaches a maximum height after 4 seconds. find the angle of projection.
2) a cricketer can throw a ball 40m vertically upwards. What is his maximum throwing range on a flat cricket field?

 

[rama_v]

this might sound easy but i dont seem to get the answer. maybe my working out is wrong anyways heres the question.
1)a body is projected with an initial velocity of 45m/s and reaches a maximum height after 4 seconds. find the angle of projection.
2) a cricketer can throw a ball 40m vertically upwards. What is his maximum throwing range on a flat cricket field?

1)
for vertical motion:
a = -g
v = -gt + Vsin@
0 = -10(4) +45sin@
40= 45sin@
therefore @ = sin^-1 (8/9)

 

[rama_v]

1)
for vertical motion:
a = -g
v = -gt + Vsin@
0 = -10(4) +45sin@
40= 45sin@
therefore @ = sin^-1 (8/9)

2) for this just derive the formula for maximum height, find then find velocity using that formula and u can then find t, time to go up. mutliplt that by two and use @ = 45 degrees and sub into the formula for maxumum range, i.e. R = V^2 sin2@/g (derive this as well)