Physics: Work and Energy

What is the product of an external force acting on an object and the displacement the force has caused?

What happens when the external force and the object's displacement are in the same direction?

What is an example of negative work?

What is true when the external force or the object's displacement is equal to zero?

What is the direction of the force and displacement in riding a bicycle?

What is the formula to find the acceleration of an object?

What is the direction of the force and displacement vectors in the positive work example?

What is the value of cos(0) in the work equation?

What is the angle between the force and displacement vectors in the zero work example?

What is the value of cos(180) in the work equation?

What is the condition for zero work?

What is the unit of work in the formula W = F · d?

What is the angle between the force and displacement vectors for positive work?

What is the purpose of drawing a free-body diagram when calculating work?

What is the difference between work in physics and work in general?

Work in Physics

Work is defined as the product of an external force acting on an object and the displacement caused by that force.
It measures the energy transferred to or from an object.

Types of Work

Positive Work: When the external force and displacement are in the same direction (e.g., pushing an object on a smooth surface, riding a bicycle, kicking a stationary ball).
Negative Work: When the external force and displacement are in opposite directions (e.g., throwing an object upward, fluid resistance to flow, pushing an object on a rough surface).
Zero Work: When the external force or displacement is zero, or when they are perpendicular to each other (e.g., carrying a box, pushing a sturdy wall, sitting on a chair).

Work Formula

Work (W) is a scalar quantity, measured in Joules (J) or Newtons-meter (Nm).
The formula is: W = F · d, where F is the force vector and d is the displacement vector.
The dot product of two vectors yields a scalar quantity.

Work and Angle

If the angle between the force and displacement vectors is between 0 and 90 degrees, the work is positive.
If the angle is between 90 and 180 degrees, the work is negative.
If the angle is 90 degrees, the work is zero.

Calculating Work

Determine the directions of the force and displacement vectors using a free-body diagram.
Calculate the force using Newton's second law (F = ma).
Calculate the work using the formula: W = F · d.

Examples

Positive Work: A 2 kg ball falls from a height of 1.5 m. The force is gravitational, and the work is positive.
Negative Work: A frictional force of 12 N acts on a box displaced by 3 m. The work is negative.
Zero Work: A chocolate box is secured in a trolley moving at 12 m/s. The force (weight) of the box is perpendicular to the displacement, so the work is zero.

Learn about the definition of work in physics, including how it's calculated and examples of positive work. Understand the concept of energy transfer and how it relates to force and displacement.