Projectile Motion Q from dot point physics (1 Viewer)

[Neha]

heyy i need help with this question

A projectile has a time of flight 7.5s and a range 1200m
calculate
(a) its horizontal velocity
(b) Its maximum height
(c) the velocity witch which it is produced

I calculated the horizontal velocity to be 160m/s but I dont know how to get the maximum height or the velocity.

 

[Forbidden.]

heyy i need help with this question

A projectile has a time of flight 7.5s and a range 1200m
calculate
(a) its horizontal velocity
(b) Its maximum height
(c) the velocity witch which it is produced

I calculated the horizontal velocity to be 160m/s but I dont know how to get the maximum height or the velocity.

Let me have a crack at it ..

b)

d_y = u_yt + (at²/2)

d_y = 0 (Total vertical displacement is zero)
0 = 7.5u_y - 275.625
7.5u_y = 275.625
u_y = 36.75

v_y² = u_y² + 2ah

v_y = 0
0 = 1350.5625 - 19.6h
19.6h = 1350.5625
h = 68.90625 ...

.: Maximum height is 68.91m




c)

u_x² + u_y² = u

(160)² + (36.75)² = 26950.5625
u = 164.1662648 ...

(c) the velocity witch which it is produced

witch velocity?
Well initial velocity is 164.17ms^-1 and the final velocity is below.

v = u + at

v = (164.1662648) + (-9.8)(7.5)
v = 90.6662648 ...

.: Final Velocity is 90.67ms^-1


I hope I am the correct.

 

[Neha]

ahh sorry i meant with not witch

I see how to do it now, thank you.

 

[Danger]

How is total vertical displacement zero?

 

[JulzMighty]

total vertical displacement is the difference between its starting position along the vertical axis and its finishing position, which is zero.

julz

 

[twilight1412]

hes finding the initial velocity so he con work it out with

v² - u² = 2as
where s is the height

since the motion is parabolic the initial and final vertical velocities are equal but opposite in direction

btw forbidden i see nothing wrong with your working =)