7.2 Linear momentum Flashcards
State the units of linear momentum
kg m s^-1 or Ns
What are the 2 quantities conserved in an explosion
The total momentum and the total energy
Objects in a perfectly in-elastic collision….
Stick together
A perfectly elastic collision is…
A collision in which the total kinetic energy of the objects involved is the same as before and after the collision
State the principle of conservation of momentum
The total momentum of a system remains the same before and after a collision - provided no external forces act on the system
State and explain if kinetic energy is conserved in an explosion
- it is not conserved
- as the total kinetic energy of the pieces of the explosion is greater that the kinetic energy of the object before the explosion
- Kinetic energy is scalar
State the equation given by the conservation of momentum for two objects that collide but don’t stick together
m1 x u1 + m2 x u2 = m1 x v1 + m2 + v2
How is linear momentum calculated
P = m x v, the product of its mass and velocity
State the formula for net force ( in terms of momentum )
Force = change in momentum / time
Force = change in ( mass x velocity ) / time
State the formula for net force when mass is constant
Force = mass x acceleration
State the equation given by the conservation of momentum for an object that explodes into 2 pieces
m x u = m1 x v1 + m2 x v2
Give examples of safety features that reduce the force of an impact
- Increasing the time for the change in momentum to reduce the force of impact
- Air bags
- Seat belts
How would the force-time graph for a car crash be different if the car has a crumple zone
- the peak would be lower
- the base of the cure would be wider
- the area under the curve will be the same
