Q22CQ Suppose you throw a rock nearly ... [FREE SOLUTION]

Chapter 2: Q22CQ (page 79)

Suppose you throw a rock nearly straight up at a coconut in a palm tree, and the rock misses on the way up but hits the coconut on the way down. Neglecting air resistance, how does the speed of the rock when it hits the coconut on the way down compare with what it would have been if it had hit the coconut on the way up? Is it more likely to dislodge the coconut on the way up or down? Explain.

Short Answer

Expert verified

Since this rock is under gravitational attraction, it has a higher probability of dislodging the coconut as it falls.

Step by step solution

Free fall due to Earth's gravity

When a rock is thrown straight at a coconut, its speed reduces owing to Earth's gravity until it reaches zero at the height of its flight. As a result, if the rock misses the coconut on its way up, it will free-fall due to Earth's gravity.

According to the law of conservation of energy, the energy, and therefore the speed of the rock, will remain the same when traveling up and down.

Total force on coconut

The difference in the coconut's weight and its force due to the rock would equal the amount of the resultant force on the coconut if the rock hit it while traveling up.

This is owing to the fact that the two forces work in opposing directions, with gravity acting downwards and the rock's force acting upwards.

However, if the rock collides with the coconut as it falls, the force it exerts on the coconut causes the amount of the resultant force on the rock to rise since it is in the direction of gravity.

As a result, because the boulder is under gravitational attraction, it has a stronger probability of dislodging the coconut as it descends.