You do 30 j of work to load a toy dart gun. however, the dart is 10 cm long and feels a frictional force of 10 n while going through the dart gunâs barrel. what is the kinetic energy of the fired dart?
a. 30 j
b. 29 j
c. 28 j
d. 27 j

Option (b) is the correct answer.

Explanation:

The given data is as follows.

          = 30 J,    l = 10 cm = 0.1 m (as 1 m = 100 cm)

               F = 10 N  

The formula to calculate the work done is as follows.

          W =

Hence, putting the given values into the above formula as follows.

                W =

                     =

                     = 1 J

As the dart loses 1 joule of energy when it goes through the barrel. Therefore, the kinetic energy it has when it comes out is calculated as follows.

              K.E = 30 - 1

                    = 29 J

Thus, we can conclude that the kinetic energy of the fired dart is 29 J.

b.a device that inputs heat into a cool object