Which action is work?
A.
Lifting a pencil.
B.
Reading a school book.
C.
Pushing a wheelbarrow.
D.
Carrying an armload of firewood.
A. Lifting a pencil.
All of the actions mentioned can be considered as work. Work is defined as the exertion of energy to accomplish a task or move an object.
A. Lifting a pencil requires exerting force against the force of gravity to raise the pencil, which can be classified as work.
B. Reading a school book involves mental effort, concentration, and processing information, which can also be considered as work.
C. Pushing a wheelbarrow requires physical effort to move the wheelbarrow, overcoming the force of friction, and moving a heavy object. This is definitely a type of work.
D. Carrying an armload of firewood involves lifting and carrying a load against gravity, which requires physical effort and energy expenditure. This action falls under the category of work as well.
To determine which action is considered work, let's review the definition of work in physics. In physics, work is defined as the product of the force applied to an object and the displacement of the object in the direction of the force.
To determine the amount of work, we need to know the force and the distance of the displacement vector. In this case, since we only have the actions described without actual numerical values, we can still determine which action requires work based on their nature.
A. Lifting a pencil: Lifting a pencil involves exerting force to overcome the gravitational force pulling down the pencil. While some effort is involved, the displacement is typically small, so the work done is relatively low compared to other actions.
B. Reading a school book: Reading a book does not involve any physical force on an object or displacement. It is an intellectual activity rather than a physical one. Therefore, it is not considered work in the context of physics.
C. Pushing a wheelbarrow: Pushing a wheelbarrow involves applying a force to overcome the friction between the wheelbarrow and the ground. The displacement in the direction of the applied force can be significant. Therefore, pushing a wheelbarrow requires work.
D. Carrying an armload of firewood: Carrying an armload of firewood involves exerting force to support the weight of the firewood against gravity as you walk or move. Similar to lifting a pencil, although the force is greater due to the weight of the firewood, the displacement is typically not very large. Hence, it requires work, but the amount of work may be relatively low.
Based on this analysis, both lifting a pencil (A) and pushing a wheelbarrow (C) involve work.