How much work is done lifting a 40 kg block up 30m on Earth?

The work done to lift the object upto 30 m on Earth is 11760 J.

Explanation:

As we all are present on the surface of the Earth , so the distance of the block moved will be considered from the surface of the Earth to 300 m distance. Work done to pull that block upside can be determined by the product of normal force with displacement.

As the mass of the block is given as 40 kg and the moving up mechanism should be done opposite in direction and equal in magnitude to the motion of acceleration due to gravity. As the acceleration due to gravity acts towards downward direction and the block is moved in upward reaction, the sign is positive for the force.

Force = mass × Acceleration due to gravity

Force = 40×9.8 = 392 N.

Then the work done is the measure of force required to move that block up on Earth.

So,  

 Work done = Force * Displacement

As it is given that the block is moved upto 30 m on Earth, the work done will be

Work done = 392*30=11760 J

Thus, the positive sign on the work done indicates that work is done on the object.

So the work done to lift the object upto 30 m on Earth is 11760 J.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.