Question

How much work does it take to lift a $180kg$ weight ${\displaystyle \frac{3}{2}}m$?

Answer 1

Hint : In order to find the solution for the given question we need to know the formula for the work done by an object. Also we need to know the relation between the mass and weight and finally using these relations we need to solve the equation obtained to get the final solution of the given question. First of all we need to find the gravitational force exerted on the object and then use the formula for work done which is the product of force and displacement.

Complete step by step solution:
Step one
The mass of the body is given as,$m=180kg$
The height to which the body is to be lifted is given as,$d={\displaystyle \frac{3}{2}}m$
We know that weight,$w=mg$
Also, we know this fact that weight is equal to the gravitational force.
$\therefore w=180\times 10=1800N$
Step two
Now, we need to calculate the work done.
We know that work done,$W=Fd$
$\Rightarrow W=1800\times {\displaystyle \frac{3}{2}}$
$\therefore W=2700J$

Therefore, the required work done to lift the object is $2700J$.

Note: The above question can also be solved by using the work energy theorem. Here, in this case the work done will be equal to the potential energy of the body. According to the work-energy theorem the total work done by the forces on an object equals to the change in its kinetic energy. We know that the kinetic energy possessed by an object is due to the motion of the object. The work done by the force is equal to the product of total applied force and the displacement of the body.