The correct option is (a).
Explanation
In physics, Work is defined as the product of the component of force in the direction of displacement and the magnitude of the displacement. Mathematically, it is expressed as \( W = F \cdot s \cdot \cos\theta \), where \( F \) is the force applied, \( s \) is the displacement, and \( \theta \) is the angle between the force and displacement vectors. Work is considered done only when a force causes displacement and the force is not perpendicular to the motion.
Statement-wise Analysis:
- Statement 1 is Correct: A bullock pulling a cart applies a force that results in the displacement of the cart in the direction of the force. Since there is both force and displacement (\( s \neq 0 \)) and the angle is not \( 90^\circ \), work is performed.
- Statement 2 is Incorrect: When a man pushes a stationary wall, he applies force, but there is no displacement (\( s = 0 \)). According to the work formula, if displacement is zero, the total work done is zero regardless of the force applied.
- Statement 3 is Incorrect: For a satellite revolving in a circular orbit, the gravitational force (centripetal force) acts towards the center of the Earth, while the instantaneous displacement is tangential to the orbit. The angle between the force and displacement is \( 90^\circ \). Since \( \cos 90^\circ = 0 \), the work done by the gravitational force is zero.
Key Takeaway:
Work in science is not merely physical exertion; it requires displacement along the direction of the force. No work is done if the object does not move or if the force acts perpendicular to the direction of motion.