Fprces Flashcards
What are forces
A force can be a push or pull on an object caused by an interaction with another object. Forces are vector quantities
What is the difference between scalar and vector
Scalar - quantities only have a magnitude - distance and speed
Vector - quantities have a magnitude and a direction eg velocity and displacement
Contact forces
Occurs when two objects are touching each other
Involves - friction, air resistance, tension and normal contact force
Non contact forces
Act at a distance not touching
Eg - gravitational force, electrostatic force, and magnetic force
Resultant force
If two or more forces act on an object along the same line, their effect is the same as if they were replaced with a single resultant force.
Sum of the magnitudes of the forces in same direction
Difference between magnitudes if forces is opposite directions
Newton’s first law
Velocity, speed, and or direction of an object will only change if a resultant force is acting on it.
Of the resultant forces of stationary item - 0 object will remain stationary
If resultant force of moving object - 0 it will continue moving at the same velocity in starlight lime
Newton’s second law
The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object. F =ma
Speed
Average speed - total distance travelled/total time taken
Velocity
Velocity of an object is its speed in a given direction
An objects velocity changes if its direction changes, even if its speed is constant
Acceleration
The change in velocity of an object per second. Vector.
Object is accelerating if its speed or direction are changing. Change in velocity/time taken - Am/s
Center of mass
Point where mass of object is concentrated.
Uniform object - direct,t in middle. Non-uniform - not in middle
Position of centre of mass is different dependent on shape of object
Equilibrium
When the forces are balanced and there is no overall force
Momentum collision
P = m x v
Momentum before = momentum after
Stopping distance
Thinking + braking
Split in two - thinking and braking distance
Stimulant drugs, depressant drugs, tiredness and visibility affect thinking distance
Braking distance can be affected by
Tyres and brakes - bad tires hot brakes, weather - rains reduce friction, car traveling faster - takes longer for car to stop
Terminal velocity
Maximum velocity that a moving object will reach
TV explanation
1- initial weight is greater then air resistance
2 - resultant force - acceleration downwards
3- as speed increases so does air resist
4- eventually the weight = air resistance
5- no overall force so no more acceleration
6 - TV is reached
How does SA affect TV
Larger SA = more air resistance, air resistance catch up with weight more quickly, less time to accelerate,
Larger SA will reach TV quicker
