Energy Equation
30/9/20
• When a force moves an object through a
distance, energy is transferred.
• Whenever something moves, something else
is supplying some sort of effort to move it.
• Whatever is putting in the effort, needs a
supply of energy (from food, fuel, etc.)
• It then transfers energy by moving the object energy is transferred to the kinetic energy
store.
• Energy transferred, force and distance are
linked by an equation:
Energy transferred = Force x Distance
E=F x d
•
•
•
•
Units are what we measure things in.
The units for Energy are Joules or J
The units for Force are Newtons or N
The units for Distance are Metres or m
Formula triangle
• We can also use formula triangles to help
us calculate things:
E
÷
F
÷
d
x
• We cover up the thing we want to find.
• And use the remaining letters to work out the answer.
• So we can get 3 equations from the
formula triangle:
Energy transferred = Force x Distance
Force = Energy transferred ÷ Distance
Distance = Energy transferred ÷ Force
Example
• A man is pulling a box along the ground
with a force of 45N to a bin which is 10m
away. What is the energy transferred?
• Energy transferred = force x distance
•
= 45 x 10
•
= 450 J
• REMEMBER THE UNIT!!!
Harder Example
• A woman uses 154J of energy to push a
shopping cart across the floor with a force
of 35N. What is the distance she pushes
the cart?
• Distance = Energy transferred ÷ force
•
•
= 154 ÷ 35
= 4.4m