Everything Science Grade 10

22.3 CHAPTER 22. MECHANICAL ENERGY

higher mass.

Checking units ESAHM

According to the equation for kinetic energy, the unit should be kg·m^2 ·s−^2. We can prove
that this unit is equal to the joule, the unit for energy.

(kg)

(

m·s−^1

) 2

=

(

kg·m·s−^2

)

·m

= N·m

(

because Force(N) =mass(kg)×acceleration

(

m·s−^2

))

= J (Work(J) =Force(N)×distance(m))

We can do the same to prove that the unit for potential energy is equal to the joule:

(kg)

(

m·s−^2

)

(m) = N·m

= J

Example 5: Mixing units & energy calculations

QUESTION

A bullet, having a mass of 150 g, is shot with a muzzle velocity of 960 m·s−^1.

Calculate its kinetic energy.

SOLUTION

Step 1:Analyse the question to determine what information is provided

452 Physics: Mechanics