Question

Tania releases a javelin 1.2 meters above the ground with an initial vertical velocity of 20 meters per second. how long will it take the javelin to hit the ground? –16t2 + 20t + 1.2 = 0 –4.9t2 + 20t + 1.2 = 0 –4.9t2 + 20t = 1.2 –4.9t2+ 1.2t + 20 = 0

Answer 1

This is an example of free fall;
For free fall the gravitational acceleration is -9.8 m/s²
From the equation;
S = ut -1/2gt², where S is the height above the ground, U is the initial vertical velocity, t is the time taken.
Therefore;
1.2 = 20t - 1/2(9.8)t²
1.2 = 20t -4.9t²
Thus; the equation is -4.9t² + 20t = 1.2, this is the appropriate answer.