Math word problem

Question

The Sears tower in Chicago is 1454 feet tall. If an object is allowed to fall freely from its top, its height is given by h(t)=-16t²+1454, where t is the number of seconds since the object was released. (This means that the velocity is zero at the moment the object is released.) When would the object reach the ground?

Answer 1

The object would reach the ground when height is 0, so we set h(t)=0 and solve for t:

 

0=-16t²+1454

16t²=1454

t²=90.875

√(t²)=±√90.875

t=±9.53

 

The object would reach the ground after approximately 9.53 seconds. (We can ignore the negative value for t because it does not make sense for time to be negative)