Question

Fig. shows a spade. It is being used to lift soil weighing 30N from the ground.

(a)    Mark the direction of the least force on the handle necessary to keep the spade balanced. 
(b)    Calculate the least force on the handle necessary to keep the spade balanced (the weight of the spade is negligible).
(c)    If the left hand was move towards the soil on the spade, would the force on the handle necessary to keep the soil balance the greater or less? Give a reason for your answer.
(d)    To which class of lever does the spade belong?

Answer 1

(a) Diagram showing the direction of application of least force on the handle:

(b) Given,load,L = 30 N

Let effort = E

Effort - arm = 20 cm

load - arm = 20 + 10 = 30 cm

Now, load x load - arm = effort x effort - arm

effort = `(30 xx 30)/20` = 45 N

(c) On moving the left hand towards the soil on the spade, the lenght of effort arm will increase and effort being inversely proportional to the lenght of effort arm, the force or effort necessary to keep the soil balanced would be less.

(d) A spade belongs to class III lever.