A woman drops a rock from a bridge to the water 17.5 m below. with what speed does the rock strike the water? a. 0 m/s
b. 18.5 m/s
c. 171m/s
d. 9.8 m/s
e. 17.5 m/s

Given :

Height from which rock is dropped, h = 17.5 m.

Initial velocity, u = 0 m/s.

To Find :

Speed does the rock strike the water.

Solution :

We know, by equation of motion :

     ......( 1 )

Here , a = g = 9.8 m/s² ( Acceleration due to gravity )

Putting all given values in 1 , we get :

Therefore, speed with rock strike the water is 18.5 m/s.

Hence, this is the required solution.

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west