Science Questions and Answers

Start Your Free Trial

When a ball is thrown down from the top of a building 75 m high it takes 3 seconds to reach the ground. If thrown upwards at the same speed how high will it go.

Expert Answers info

Tushar Chandra eNotes educator | Certified Educator

calendarEducator since 2010

write12,551 answers

starTop subjects are Math, Science, and Business

When the ball is thrown downwards it accelerates downwards due to the gravitational force of attraction of the Earth at 9.8 m/s^2. If an object has an initial velocity of u m/s and it is accelerating at a m/s^2, the distance traveled by the object in time t is given by D = u*t + (1/2)*a*t^2

Substituting the values given in the question,

75 = u*3 + (1/2)*9.8*9

=> u = 25 - 14.7

=> u = 10.3 m/s

If the ball is thrown upwards at 10.3 m/s, the height to which it rises is equal to h where (1/2)*(10.3)^2 = 9.8*h

=> h = 5.41

The ball rises to a height of 5.41 m

check Approved by eNotes Editorial