You are here:

# Calculus/Algebra

Question
Susan throws a softball upward into the air at a speed of 32 feet per second from a 104-foot platform. The distance upward that the ball travels is given by the function d(t)=-16t^2+32t+104. What is the maximum height of the softball? How many seconds does it take to reach the ground after first being thrown upward?

When the softball attains maximum height, d(t)/ dt =0
ie  -32t +32 =0

t=1 s

When t=1, height = -16 (1)^2 +32 (1) +104 =120 feet (shown)

When it reaches the ground, height above ground = 0 ft

ie  -16 t^2 +32t +104 =0

2t^2 -4t - 13 =0    (dividing both sides by -8)

Hence,  t= 3.74s  (shown)   or  t=-1.74s (rejected)

Hope this helps. Peace.

Calculus

Volunteer

#### Frederick Koh

##### Expertise

I can answer questions concerning calculus, complex numbers, vectors, statistics , algebra and trigonometry for the O level, A level and 1st/2nd year college math/engineering student.

##### Experience

More than 7 years of experience helping out in various homework forums. Latest Presence is over at http://www.thestudentroom.co.uk/ . You can also visit my main maths website http://www.whitegroupmaths.com where I have designed "question locker" vaults to store tons of fully worked math problems. A second one is currently being built. Peace.

Organizations
IEEE(Institute of Electrical and Electronics Engineers )

Education/Credentials
Former straight As A level student from HCJC (aka HCI); scored distinctions in both C and Further Mathematics B Eng (Hons) From The National University Of Singapore (NUS) B Sc (Hons) From University of London International (Grad Route)