A boy raises a box with a weight of 120 N from a height of 2 m. The work done by him is ________.
240 J
Understanding Work Done in Physics
The question asks us to calculate the work done by a boy when he raises a box of a certain weight to a specific height. In physics, work done is a measure of the energy transferred when a force causes an object to move over a distance.
What is Work Done?
Work done (W) is defined as the product of the force (F) applied to an object and the distance (d) over which the object moves in the direction of the force. The formula for work done when the force is applied in the direction of motion is:
\[W = F \times d\]
Where:
- \(W\) is the work done (measured in Joules, J)
- \(F\) is the force applied (measured in Newtons, N)
- \(d\) is the distance moved in the direction of the force (measured in meters, m)
Analyzing the Problem
In this problem, the boy is raising a box. To raise the box against gravity, the boy must apply a force equal to the weight of the box. The box is moved upwards to a certain height.
- The weight of the box is given as 120 N. This is the force (\(F\)) the boy applies upwards to lift the box.
- The height the box is raised to is given as 2 m. This is the distance (\(d\)) over which the force acts in the direction of motion (upwards).
Calculating the Work Done
Using the formula for work done, we can plug in the given values:
\[W = F \times d\]
\[W = 120 \text{ N} \times 2 \text{ m}\]
\[W = 240 \text{ J}\]
Therefore, the work done by the boy in raising the box is 240 Joules.
Summary of Calculation
| Quantity | Value | Unit |
|---|---|---|
| Force (\(F\)) | 120 | N |
| Distance (\(d\)) | 2 | m |
| Work Done (\(W\)) | 240 | J |
The calculation shows that the work done is 240 J.
Revision Table: Work, Force, and Distance
| Concept | Definition | Formula | Units |
|---|---|---|---|
| Work Done | Energy transferred when a force moves an object over a distance. | \(W = F \times d\) (when force is parallel to displacement) | Joules (J) |
| Force | A push or pull that can change an object's motion. | Varies (e.g., Weight = mass x gravity) | Newtons (N) |
| Distance (Displacement) | The change in position of an object. | \(d\) | Meters (m) |
Additional Information on Work Done
It's important to note that work is only done when a force causes displacement. If the boy held the box at the height of 2m without moving it further, no additional work would be done by him (although work was done to lift it to that height). Also, if the force is applied perpendicular to the direction of motion, no work is done by that force.
In this case, the force (upwards) and the displacement (upwards) are in the same direction, so the full force contributes to the work done.
Important Questions from Work Power and Energy
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?
Work done by conservative force is equal to
