need Help with quadratic problem

Question

A brick is dropped from a building

formula is h(t)=Vt+at ^2

V=velocity, t=time and a=acceleration

initial velocity is given as 0m/s. Fall time is 3.5secs

 

Q1:what is height of the building 

Q2:time the brick is in the air if velocity is changed to 5m/s

Answer 1

In the metric system the acceleration due to gravity is 9.8 m/sec². BUT the equation left out the factor of (1/2)!

 

Using the values given in the problem: h(3.5) = 4.9 * 12.25 =  60.025m

 

 

The second part of the question depends on whether the brick was thrown upwards or downwards with initial velocity of 5ms.  The equation will be 0 = 60.025 ± 5t - 4.9t² where you choose the + sign if the brick is thrown upwards and the minus sign if downwards.  Use the quadratic formula to solve and remember that the quadratic formula expects that the sign of the squared term will be +.