Thread: Initial velocity of projectile launced from above origin

I understand how to calculate the initial velocity of an object launched at an angle from the normal, but suppose i have a projectile launched at a 45 degree angle 10 meters above the X-axis and the projectile lands on the X-axis 100 meters from where it was launched. How do I calculate the initial velocity of the projectile in this hypothetical?

Originally Posted by Mr. Rogers

I understand how to calculate the initial velocity of an object launched at an angle from the normal, but suppose i have a projectile launched at a 45 degree angle 10 meters above the X-axis and the projectile lands on the X-axis 100 meters from where it was launched. How do I calculate the initial velocity of the projectile in this hypothetical?

Motion in the horizontal direction:

Initial velocity m/s.
Acceleration .
Displacement = 100 m
Therefore t = ..... (A)

Motion in the vertical direction (take upwards as positive and take the origin to be where the object is launched):

Initial velocity m/s.
Acceleration .
Displacement = -10 m.
t = expression found above (A).

Substitute all this into and solve for u.