High School

A rock is thrown off a vertical cliff at an angle of 58.9 degrees above the horizontal. The cliff is 60.9 meters high, and the ground extends horizontally from the base. The initial speed of the rock is 26.4 m/s. Neglect air resistance.

How high above the ground, in meters, is the rock 1.57 seconds before it hits the ground?

Answer :

Final answer:

Given the projectile motion problem, the height of the rock 1.57 seconds before it hits the ground is calculated to be approximately 109.29 meters

Explanation:

This is a problem of kinematics, where we need to compute the height of a rock given information about its initial velocity, angle of projection, and time before hitting the ground. The key equation here is H = V * t - 0.5 * g * t2.

The first step is finding the overall time of flight, which is (2 * V * sinθ) / g; plugging the values in (2 * 26.4 * sin58.9) / 9.8 = 5.03s. So, 1.57 seconds before hitting the ground would be at t = 5.03 - 1.57 = 3.46s.

To find the vertical height at this moment, plug the values into the equation: H = 26.4 * sin58.9 * 3.46 - 0.5 * 9.8 * 3.462 = 48.39m. Adding the height of the cliff, we get 60.9 + 48.39 = 109.29m. So, the rock is 109.29 meters above the ground 1.57 seconds before it hits the ground.

Learn more about Projectile Motion here:

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