P10 Force And Motion Flashcards
Force =
Mass x acceleration
Newton’s second law
The acceleration of an object is proportional to the resultant force on the object and inversly proportional to the mass of the object
Inertia
The tendency of an object to oppose a change of state of motion.
Inertial mass =
Force / acceleration
1 kg =
10 N
Weight =
Mass x gravitational field strength
Terminal velocity
The maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces.
Stopping distance =
Thinking distance + braking distance
Thinking distance
The distance travelled in the time it takes for the driver to react. Thinking distance = speed x reaction time
Braking distance
The distance travelled by the vehicle during the time the braking force acts
Deceleration =
v² = u² + 2as
How to calculate braking force
F=ma
Momentum (p) =
Mass (m) x velocity (v)
Unit for momentum
Kg m /s
Momentum is a _________ quantity
Vector
Conservation of momentum
In a closed system, the total momentum before the event is equal to the total momentum after the event
The longer the impact time…
The more the impact force is reduced
Impact force=
(Mass x change of velocity) / time
What do car safety features such as crumple zones and side bars do?
They increase the impact time and so reduce the impact force on the car
How do helmets and cusioned surfaces ensure safety?
They reduce impact force by increasing the impact time
How do seat belts and air bags ensure safety?
They spread the force across the chest and increase the impact time
What is an elastic object?
An object that returns to its original shape when the forces deforming it have been removed
What is extension?
The increase of length from the original
A straight line going through the origin on a weight-extension graph represents?
The weight is directly proportional to the extension of the spring
Hooke’s law
The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded
Hooke’s law equation
F = k x e
Unit for spring constant
N/m
