In which of the following cases is the work done negative?
Force and displacement are between 90° and 180°
Work done is defined as \(W = F \cdot s \cdot \cos\theta\), where \(\theta\) is the angle between the force and the displacement.
The sign of the work depends entirely on \(\cos\theta\), since force magnitude and displacement magnitude are always positive.
When \(\theta\) lies between 90° and 180°, \(\cos\theta\) is negative, so the work done becomes negative (the force opposes the motion, e.g. friction).
For 0° to 90°, \(\cos\theta\) is positive (positive work); at exactly 90° the force and displacement are perpendicular and \(\cos 90° = 0\), giving zero work.
Hence, the work done is negative when the force and displacement are between 90° and 180°.
Similar Questions
- Which energy of the wind does a windmill use?
The conversion of chemical energy into electrical energy and then into light and thermal energy occurs in which of the following cases?
The commercial unit of electrical energy is kilowatt hour (kWh) and 1 kWh is equal to __________.
Electrical energy can be calculated using which of the following formulas?
When a stretched rubber band is released, its stored potential energy is converted into which form of energy?
In a classroom discussion about the measurement of work and energy, students are asked to identify the correct SI unit and dimensional formula for these quantities. Which option best represents units for both work or energy?
Which quantities influence the kinetic energy of a moving body?
Important Questions from Work Power and Energy
A boy raises a box with a weight of 120 N from a height of 2 m. The work done by him is ________.
While releasing the arrow from a stretched bow, the Potential Energy of the bow is converted into?
Which is the main source of almost all energy on Earth?
Area under constant velocity – time curve equals ________ of the object over a given time interval.
If a body of mass is m, linear momentum is p and kinetic energy is K, then which of the following expressions is true?
