Q. 2 E4.1( 9 Votes )

# Choose one or more correct alternatives.While dragging or lifting an object, negative work is done byi. the applied forceii. gravitational forceiii. frictional forceiv. reaction force

Option (ii) gravitational force and (iii) Frictional Force

Explanation:

Work done by a force on an object is negative when direction of force acting on object and displacement of object are in exactly opposite direction, or direction of displacement makes 1800 with direction of applied force because we know work done on an object due to a force is given by relation

W = F× s × cos𝜽

Where W is the work done due to force F in displacing object by S , 𝜽 is the angle between force and displacement.

angle between force and displacemnt is

𝜽 = 1800

So, work done will be

W = F× s × cos1800

From trigonometry we know, cos1800 = -1

So putting the value we get work done as

W = -FS

i.e. work done is negative when direction of displacement and applied force are opposite

Now when an object is lifted from ground, gravitational force due to earth in acting in downward direction and displacement is in upward direction due to applied force

as Shown in figure Since Gravitational force and direction of displacement are in opposite direction work done by gravitational force is negative

Now when an object is dragged Frictional force is trying to oppose the motion and hence acts in direction of applied force and displacement

As shown in figure As displacement of object and applied frictional force are in opposite direction work done by frictional force is negative.

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Let's Calculate Workdone by a Body42 mins  Foundation | Rapid Fire Quiz36 mins  Introduction to Work40 mins  Foundation | Let us Understand Law of Conservation of Energy44 mins  NCERT | Introduction to Work39 mins  Quiz | Lets Solve the NumericalsFREE Class  Conservation of Mass-Energy41 mins  How Does Barometer Work?36 mins  Cell Organelles of Energy Metabolism49 mins  Champ Quiz | 2-Dimension( Coordinate geometry )36 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 