Question

A volcano launches a lava bomb straight upward with an initial speed of 28m/s. Taking upward to be the positive direction,find speed and direction of motion of the lava bomb . a) 2.0seconds and b)3.0seconds after it is launched

Answer 1

The equation to be used here would be:

v = u - gt
 where u is the initial speed, g is the acceleration due to gravity and t is the time it takes

a) u = 28 m/s, g = 9.8 m/s^2, t = 2s
 
v = 28 m/s - 9.8 m/s^2 * 2s = 8.4 m/s after 2 s the lava bomb is still travelling upwards
 
b) u = 28 m/s g = 9.8 m/s^2 t = 3s
 
v = 28 m/s - 9.8 m/s^2 * 3s = -1.4 m/s after 3s the lave bomb is travelling downwards