Question

A projectile is thrown with an initial speed of 20 m/s at an angle 30 degrees above

the horizontal.
a. What is the maximum height of the projectile?
b. What is the speed of the projectile 2 seconds after being launched?

Answer 1

Initial velocity u = 20 m/s

Initial horizontal velocity = 20 cos30° = 20 * 0.866 = 17.32 m/sec.

Initial vertical velocity = 20 sin30° = 20 * 1/2 = 10 m/sec.

time taken t = u/g = 10/10 =1 sec. ( approximating g to 10m/sec^2)

Maximum height h = ut + 1/2 * g * t^2

h = 10 *1 - 1/2 * 10 * 1* 1

h = 10 - 5 = 5 metres.

Total time in air = 2t = 2 seconds.