Questions and Answers
What is the definition of work done by a force?
What is the unit of work?
What is the work done when a force is acting perpendicular to the direction of displacement?
What is the work done by an external force of 50 N on a mass with displacement of 5 m when the angle between the force and displacement is 0°?
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How is the work done by frictional force calculated when it acts opposite to displacement?
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Study Notes
Work
- Defined as the product of force and displacement in the direction of that force.
- Work is classified as a scalar quantity, which means it has magnitude but no direction.
- Mathematically represented by the equation:
( W = F \cdot S = |F| |S| \cos \theta )
Units and Dimensions of Work
- The unit of work is Newton-meter (Nm) or Joule (J).
- The dimensional formula for work is ( ML^2T^{-2} ).
Cases of Work
-
Force in the Direction of Displacement (θ = 0°):
Work is maximized, calculated as:
( W = F \cdot S \cos 0° = F \cdot S ) -
Force Perpendicular to Displacement (θ = 90°):
No work is done since the direction of force does not contribute to displacement:
( W = F \cdot S \cos 90° = 0 ) -
Force Opposite to Displacement (θ = 180°):
Work is negative, indicating that the force opposes motion:
( W = F \cdot S \cos 180° = -F \cdot S )
Example Calculation of Work
-
Problem concerns a mass of 10 kg with a displacement of 5 m.
-
External Force: 50 N with an angle of 0° to the displacement.
Work done by external force is calculated as:
( W_{ext} = 50 \times 5 \times 1 = 250 , J ) -
Frictional Force: 10 N with an angle of 180° to the displacement.
Work done by frictional force is calculated as:
( W_{friction} = 10 \times 5 \times (-1) = -50 , J )
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Description
Test your knowledge on the concepts of work, power, and energy. This quiz covers the definitions, formulas, and units related to work, as well as different cases of work involved in force and displacement. Ideal for students studying physics.
