841905
P2.3 Work, Energy and Momentum
- Energy and Work
- Working out
- When an
object is
moved by a
force, work is
done
- Energy
transferred =
work done
- work done (J) =
Force (N) X
Distance moved
(m)
- When an
object is
moved by a
force, work is
done
- Friction
- work done to
overcome friction
is transferred into
energy by heating
- work done to
overcome friction
is transferred into
energy by heating
- Working out
- Gravitational
Potential Energy
- energy stored in an object
because of its position in the field
- change in gravitational
energy (J) = mass (kg)
X gravitational strength
(N/kg) X change of
height (m)
- Power (W) =
Energy (J) /
Time (s)
- energy stored in an object
because of its position in the field
- Kinetic energy
- Depends on mass and speed
- Kinetic energy (J)
= 0.5 X Mass (kg)
X Speed (s) ^2
- Kinetic energy
recovery
systems
(KERS) in
vehicles store
energy for later
- Elastic potential energy
- Can be transferred
to kinetic energy
- energy stored
in elastic when
force is exerted
to deform it
- Can be transferred
to kinetic energy
- Depends on mass and speed
- Momentum
- momentum of a moving object = mass X velocity
- Law of conservation of
momentum states in a
closed system momentum
before and after an event will
be equal
- Momentum is
conserved in
any collision
- momentum of a moving object = mass X velocity
- Explosions
- mass of A X velocity of a
= - (mass of B X Velocity
of B)
- This is why guns have recoil
- mass of A X velocity of a
= - (mass of B X Velocity
of B)
- Impact forces
- Crumple zones are at
both ends of the car (at
the front to reduce
momentum and at the
back to increase)
- The longer the
impact time, the
less impact force
- When things collide,
they exert equal and
opposite forces on
each other
- Crumple zones are at
both ends of the car (at
the front to reduce
momentum and at the
back to increase)
- Car Safety
- Seat belts and air
bags increase SA
and increase
impact time
- Crumple zones increase impact time
- We can use conservation of
momentum to find the speed
of the car before impact
- Seat belts and air
bags increase SA
and increase
impact time
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