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Chapter 2: Q. 13 (page 58)

A rock is thrown (not dropped) straight down from a bridge into the

river below. At each of the following instants, is the magnitude of the rock’s acceleration greater than g, equal to g, less than g, or 0? Explain.

a. Immediately after being released.

b. Just before hitting the water.

Short Answer

Expert verified

a. Immediately after being released, the rock's magnitude of acceleration remains the same i.e. equal to g.

b. Just before hitting the water, the magnitude of the acceleration of the rock remains the same i.e. equal to g.

Step by step solution

01

Part (a) Step 1: Introduction

The pull of gravity that causes the acceleration of gravity is a constant. It is equal for all the objects on the surface of the earth.

02

Explanation

When the rock is thrown into the river from a bridge, there must be a positive initial velocity of the rock. Owing to gravitational effect, the acceleration of the rock should be equal to gravitational acceleration g soon after being released.

03

Part (b) Step 1: Introduction

While moving down into the river, there is no other force that resist or increase the speed of the rock. Also, the magnitude of gravity pull remains the same before it hits the water surface that is equal to g.

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