Which of the following statements is correct about negative work done?
Work done is negative when the force acts opposite to the direction of displacement.
The correct answer is option 4: Work done is negative when the force acts opposite to the direction of displacement.
Understanding Work Done:
Work done is defined as the product of the force applied on an object and the displacement of the object in the direction of the force. Mathematically, it's represented as:
\(W = Fd\cos(\theta)\)
where:
- \(W\) represents the work done
- \(F\) represents the magnitude of the force
- \(d\) represents the magnitude of the displacement
- \(\theta\) represents the angle between the force vector and the displacement vector
Analyzing the Options:
- Option 1 is incorrect. Work done can be negative.
- Option 2 is incorrect. When the force and displacement are in the same direction, \(\theta = 0\), and \(\cos(0) = 1\). This results in positive work done.
- Option 3 is incorrect. When the force is perpendicular to the displacement, \(\theta = 90^\circ\), and \(\cos(90^\circ) = 0\). This results in zero work done.
- Option 4 is correct. When the force acts opposite to the direction of displacement, \(\theta = 180^\circ\), and \(\cos(180^\circ) = -1\). This results in negative work done. This implies that the force is resisting the motion.
Example: Imagine lifting a box (positive work) versus lowering a box (negative work). In lowering, the force you apply is opposite the direction of the box's displacement.
Similar Questions
- The work done by a 10 Newton force acting on a body, which results in the displacement of 2 m in the direction of the force, is __________.
- An object of mass 1 kg is moving with a velocity 10 m/s. Find the kinetic energy of the object.
- The efficiency of a machine can never be ______.
- In practice, the work output of a machine is ______ the work input due to the effect of friction.
- How much energy is used by an 80% efficient, 2kW motor running at a peak load for 5 hours?
- A pump is required to lift 600 kg of water per minute from a well 25m deep and to eject it with a speed of 50 m/s. If \(g = 10 \text{ m/s}^2\), the power required to perform the above task is
- A lorry and a car moving with the same kinetic energy are brought to rest by applying the same retarding force. Then:
- In practice, the work output of a machine is always less than the work input due to the effect of ______.
- Ideal machines are those imaginary machines which are ______.
- The efficiency of a simple machine is defined as ______.
Important Questions from Work Power and Energy
Which of the following is an example of potential energy?
_______ is one of the chemical used to produce Ocean Thermal Energy.
A body of mass 2kg is thrown up vertically with a kinetic energy of 500J. If the acceleration due to gravity is 10 m/s2, the height at which the kinetic energy of the body becomes half of the original values is _____
Arjun has a mass of 50 kg, he eats banana of 1000 calories. If this energy is used up to lift him from the ground, the height to which he can climb is _______. Take g = 10 m/s2 and 1 calories = 4.2 Joule.
When a body of mass 'm' attains a velocity 'v' from rest in time 't', then kinetic energy of translation is:
