The question asks for the definition of work in physics. We need to recall the standard definition of work and compare it with the given options.
A) Force applied over a distance correctly captures the essence of work in physics. Work is done when a force causes an object to move a certain distance. This aligns with the formula \(W = F \times d\).
To determine the work done by the centripetal force, we need to understand the definition of work in physics and the characteristics of centripetal force and displacement in circular motion.
Correct Option: B) Zero
The question asks for the SI unit of work. To answer this, we need to recall the definition of work in physics and its standard unit in the International System of Units (SI).
Correct Option: A) Joule is the SI unit of work. One Joule is defined as the amount of work done when a force of one Newton displaces an object by one meter in the direction of the force.
The question asks for the definition of work in physics. Work is a scalar quantity that describes the energy transferred to or from an object by applying a force that causes displacement. We need to recall the standard physics definition of work.
A) Force and displacement in the same direction — This is the precise definition of work when the force is applied in the direction of motion. More generally, it's the component of the force in the direction of displacement multiplied by the displacement, or the component of displacement in the direction of force multiplied by the force. When they are in the same direction, \( \cos \theta = 1 \), and work is simply the product of force and displacement magnitudes.
The question asks to identify the true statement regarding work done by a force. We need to recall the definition and formula for work done and analyze each option based on this fundamental concept.
Correct Option: B) If the force is perpendicular to the displacement, no work is done
To determine the work done by gravity, we need to consider the definition of work in physics, which involves the force applied and the displacement in the direction of the force. The key is to analyze the direction of the gravitational force relative to the direction of the book's displacement.
where \(F\) is the magnitude of the force, \(d\) is the magnitude of the displacement, and \(\theta\) is the angle between the force vector and the displacement vector.
Since \(\cos(180^\circ) = -1\), the work done by gravity is:
\[ W = Fd(-1) = -Fd \]This shows that the work done by gravity is negative.
A) Negative — As derived, when an object is moved against the direction of the gravitational force (i.e., lifted upwards), the work done by gravity is negative because the angle between the force of gravity and the displacement is \(180^\circ\).