P2 Flashcards
When two forces interact?
Exert equal and opposite forces on each other.
Resultant force?
Is a single force that has same effect as all the forces acting on an object. If object accelerating, resultant force acting on it.
When resultant force at zero?
Object at rest, stay at rest.
Object moving, carry on moving in same speed and same direction.
If resultant force is not zero?
Object at rest, will accelerate in direction of the resultant force.
Object moving in same direction as resultant force, accelerate in that direction.
Object moving in opposite direction to resultant force, will decelerate.
Stopping distance?
Distance travel during driver’s thinking distance (reaction time increased if tired or under alcohol/drug influence) plus the braking distance (distance travelled under breaking force increased by bad weather, poor maintain roads, condition of car e.g. Worn tires).
If an object falls freely?
Resultant force acting on it is force of gravity. Will make object close to Earth’s surface accelerate at 10m/s.
What happens when an object drops in fluid?
Fluid exerts a drag force on object, resisting its motion. Faster object falls, bigger drag force becomes, until equal to weight of object. Resultant force now at zero, body stops accelerating. Moves at a constant velocity called terminal velocity.
An elastic object?
Regains original shape when forces deforming it are removed.
If we plot a graph of extension against force applied for a spring?
Obtain straight line passing through origin. Tells us extension directly proportional to force applied. Apply too big a force, line curves as we have exceeded limit of proportionality.
Hooke’s law states?
The extension is directly proportional to the force applied, provided limit of proportionality is not exceeded.
Forces measured in?
Newtons N. (Force can change objects shape, motion or state of rest).
