Question

A student stands on the edge of a cliff that is 300 m high and kicks a rock horizontally. 7.8 seconds later, the rock hits the ground. If the rock lands 50 meters from the base of the cliff, what was the rock's horizontal velocity?

Answer 1

6.65m/s

Step-by-step explanation:

Using the equation of motion

S = ut + 1/2gt²

S is the height of fall

t is the time

u is the horizontal velocity

g is the acceleration due to gravity

Given

S = 300 + 50

S = 350m

t = 7.8seconds

g = 9.8m/s^2

Get S

S = 7.8u + 1/2(9.8)(7.8)²

S = 7.8u + 298.116

350 = 7.8u + 298.116

7.8u = 350 - 298.116

7.8u = 51.884

u = 51.884/7.8

u = 6.65m/s

Hence the rock's horizontal velocity was 6.65m/s