A pelican flying along a horizontal path drops a fish from a height of 4.6 m, the fish travels 6.8 m horizontally before it hits the water below. What was the pelican's speed?
To determine the pelican's initial speed we first need to determine the time that elapsed before the fish hit the water.
The fish was dropped from a height of 4.6 m and it only had a horizontal velocity initially. The acceleration due to gravity is 9.8 m/s^2. The relation between the initial velocity, acceleration, time and distance traveled for an object is s = u*t + (1/2)a*t^2
=> 4.6 = 0*t + (1/2)*9.8*t^2
=> t^2 = 4.6*2/9.8
=> t = (sqrt 46)/7 s
The fish hit the water after (sqrt 46)/7 seconds. In this duration of time it traveled 6.8 m horizontally.
The horizontal speed of the fish was 6.8*7/sqrt 46 = 7.01 m/s.
As the fish had the same horizontal speed as the pelican that dropped it, the speed of the pelican was also 7.01 m/s