When a surfer rides an ocean wave on her surfboard, she is actually riding on. a. a crest that is toppling over. b. a trough of the wave. c. the rest position of the wave. d. a region of rarefaction.

A. a crest that is toppling over.

Explanation:

As we know that at the position of crest in a wave the velocity of motion of molecules is the least velocity or zero velocity

So as the surfer needs the stability he need a point of least velocity and maximum stability

So in that case he has to travel at the position of crest where he can obtain maximum stability and then his speed will be same as the speed of wave propagation in the direction of wave

so here correct answer would be

A. a crest that is toppling over.

initial speed when it is dropped is 150 ft/s

now at the same moment the acceleration due to gravity is perpendicular to its velocity

so as we know that

now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity

while tangential acceleration at the same moment will be zero

so

now radius of curvature is given as

so the radius of curvature just after it is dropped is 703.125 ft