Question

7. A spring balance reads force in Newton. The scale is 20 cm long and reads from 0 to

Answer 1

Answer:

The potential  energy when it reads 40 N is $PE = 5.33 \ J$

Explanation:

From the question we are told that

   The lowest reading of the spring balance is  0 N and this is at  0 cm = 0 m

   The height reading of the spring balance is 60 N  and this is at 20 cm =  0.20 m

   Generally the length corresponding to the reading of 40 N is mathematically represented as

       $d = \frac{40 * 0.20 }{60 }$

=>    $d = 0.133 \ m$

Generally the potential  energy is mathematically represented as

      $PE = m * g * d$

Here

     $F = mg = 40 N$

So  

     $PE = 40 * 0.133$

=>  $PE = 5.33 \ J$