Consider this situation: A team of landscapers pull an unplanted tree across the lawn. Of the forces listed, identify which act upon the tree.
The Correct Answer and Explanation is:
Correct Answer:
The forces that act upon the tree in this situation are:
- Applied Force – the landscapers pulling the tree.
- Gravitational Force – the weight of the tree due to gravity.
- Normal Force – the support force from the ground acting upward on the tree.
- Frictional Force – resistance from the grass or ground opposing the motion of the tree.
- Air Resistance (Drag) – a minor force opposing the motion through air (though typically negligible at low speeds).
Explanation
In this scenario, several forces act upon the tree as it is dragged across the lawn. Understanding these forces helps us analyze the tree’s motion in terms of basic physics principles, especially Newton’s laws.
First, the applied force is the direct physical pull exerted by the landscapers. This is the primary force causing the tree to move across the lawn.
Next, gravitational force acts vertically downward on the tree. This is the force of Earth’s gravity pulling the tree toward the ground, equal to the tree’s mass times the gravitational acceleration (usually 9.8 m/s²).
Opposing gravity is the normal force, which is exerted by the ground upward. This force balances the downward gravitational pull, preventing the tree from sinking into the Earth. The normal force is equal in magnitude and opposite in direction to the vertical component of the gravitational force when the tree is on level ground.
As the tree is dragged, it encounters frictional force from the contact with the ground surface. This force acts in the opposite direction of the pull and resists the motion. Its magnitude depends on the surface texture and the weight of the tree.
Finally, though usually minor in such cases, air resistance (or drag) also acts on the tree. It opposes motion through the air, but for a heavy, slowly moving object like a tree, it is often negligible unless the tree is being moved at high speed or in strong wind.
Together, these forces determine the net force on the tree and influence how it accelerates, moves, or comes to rest.
