P4 - Change In Momentum Flashcards
What causes the change in momentum?
When a resultant force acts on an object this causes the momentum to change in the direction of the force.
What is the change of momentum proportional to?
The size of the force and the time it acts for
What is the change of momentum equation?
Change of momentum (kg) = resultant force (N) x time for which force acts (s)
What happens when momentum changes fast?
The forces on the body will be very large due to the fast nature of the momentum changing, this means that injury is more likely.
What is the equation for force?
Force = change in momentum / time
The greater the time for a change in momentum…
The smaller the force as there is more time for the momentum to change.
What is the difference between the momentum in controlled breaking in the car and the momentum in a collision?
In a controlled breaking, the forces acting on your body are small as the momentum changes slowly, reducing injury. In a collision the mass and velocity stay the same so the momentum change can’t be affected. However, the average force can be lowered by slowing the object down.
What safety features in the car increase in the collision time to reduce the forces on the passengers?
Crumple zones crumple on impact, increasing the time taken for the car to stop.
Airbags slow you down more gradually.
Seatbelt’s stretch slightly, increasing the time taken for the wearer to stop. This reduces the forces acting on the chest.
Cycle and motorcycle helmets provide padding that increases the time taken for your head to come to a stop if it gets hit.
What does a curve in a displacement time graph show ?
This shows acceleration or deceleration due to unbalanced forces.
What does a changing direction in a displacement time graph show?
For a ball it would show that the forces are balancing as the reaction force from the ground is causing the ball to bounce.
What does a curve in a displacement time graph show ?
This shows acceleration or deceleration due to unbalanced forces.
What does a changing direction in a displacement time graph show?
For a ball it would show that the forces are balancing as the reaction force from the ground is causing the ball to bounce.
