# Exploring Forces Acting on a Rock Dropped Off a Cliff

• cheerspens
In summary, The only force acting on the rock at the moment of release is gravity downward, and as it falls there is air resistance upward and a greater force of gravity downward. When the rock hits its terminal velocity, the forces of gravity and air resistance become equal and opposite. Atmospheric pressure is not taken into consideration.
cheerspens

## Homework Statement

I have to draw a force diagram for a rock dropped off a cliff at the moment of release.
Is there any force acting upward on the rock at the moment of release?

none

## The Attempt at a Solution

I know the force of gravity acts downward on the rock. My thinking is that the only force acting on the rock at the moment of release is gravity downward, then as it falls there is air resistance upward and a greater force of gravity downward. When a rock hits it's terminal velocity however the forces of gravity and air resistance are equal. Is this correct?

Hi cheerspens!
cheerspens said:
I know the force of gravity acts downward on the rock. My thinking is that the only force acting on the rock at the moment of release is gravity downward, then as it falls there is air resistance upward and a greater force of gravity downward. When a rock hits it's terminal velocity however the forces of gravity and air resistance are equal. Is this correct?

Equal and opposite!

Otherwise, completely correct!

(i assume you're supposed to ignore the atmospheric pressure all round the rock )

## 1. What is the force of gravity acting on the rock?

The force of gravity acting on the rock is its weight, which is equal to its mass multiplied by the acceleration due to gravity.

## 2. How does air resistance affect the rock's fall?

As the rock falls, it experiences air resistance, which is a force that opposes its motion. This force increases as the rock's velocity increases and can eventually balance out the force of gravity, causing the rock to reach a maximum velocity called terminal velocity.

## 3. What other forces may act on the rock during its fall?

Other forces that may act on the rock include the normal force from the surface it lands on, friction, and any external forces such as wind or air currents.

## 4. How does the shape and weight of the rock affect its fall?

The shape and weight of the rock can affect its fall in several ways. A heavier rock will experience a greater force of gravity, causing it to fall faster. The shape of the rock can also affect its air resistance, with more streamlined shapes experiencing less air resistance and reaching a higher terminal velocity.

## 5. Can the force of gravity change during the rock's fall?

No, the force of gravity remains constant during the rock's fall. However, the force of air resistance and other external forces may change, affecting the overall forces acting on the rock.

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