Forces Flashcards
What is a force?
> It is a push or Pull factor, that acts on an object due to its interaction with another object.
What is a contact force and give some examples?
> Requires two objects to be touching.
E.g. Friction, air resistance, Tension
What is a non-contact force and give some examples?
> Doesn’t require objects to be touching.
E.g. Gravitational, electrostatic, magnetic
What is a scalar quantity with examples?
> Have only magnitude
E.g. speed, mass, distance, temperature, time
What is a vector quantity with examples?
> It has magnitude and direction
E.g. Displacement,momentum,velocity,ecceleration,force
What is the resultant force?
> Resultant Force=Overall force on an object
Equilibrium is all forces=0
What is Elastic deformation
When an object returns to its original shape.
What is inelastic deformation?
> When an objects stays deformed.
What is Extension?
Increase in length of a spring when its stretched.
What is the formula which involved Force,spring and extension?
F=Ke
Force = Spring X Extension
(N) (N/m) (M)
What is Hooke’s Law?
Force is Directly Proportional to Extension
How do you workout Elastic Potential Energy?
Ee = 0.5 k e^2
Elastic Potential Energy = 0.5 X Sprung constant X Extension^2
Describe a method used to investigate the stretching of a Spring?
- Set up a clamp stand with a clam and hang the spring from the clamp
*Use a second clamp and boss to fix a (half) metre rule alongside the spring
*Record the ruler reading that is level with the bottom of the spring
*Hang a 1 N / a known weight from the bottom of the spring
*Record the new position of the bottom of the spring
*Calculate the extension of the spring and measure the extension of the spring
*Add further weights to the spring so the force increases 1 N at a
time up to 5 N
Formula to workout velocity?
Displacement
Velocity = ————————-
Time Taken
Typical Everyday speeds?
Walking=1.5 m/s
Cycling=6 m/s
Running=3 m/s
Train=5 m/s
Car=25 m/s
Train=55 m/s
What is acceleration?
> Rate of change in velocity.
(How quickly something speeds up/slows down).
What is the equation for acceleration?
. . . Change in Velocity (m/s)
Acceleration= ————————————–
Time (s)
What is the equation for acceleration?
2as= v’2-u’2
2(Acceleration + Distance) = Final V - Initial V
Describe the terminal velocity of objects falling?
> At the start when they fall off, the force of gravity is much more than the frictional force, so they accelerate.
As the speed increases friction builds up
This gradually decreases the acceleration until eventually the frictional force is equal to the accelerating force
It will have reached it’s maximum speed
Describe the terminal velocity of a skydiver falling?
> Initially, the upwards air resistance is very small because the skydiver isn’t falling very quickly
As they speed up, the air resistance increases, eventually growing large enough to balance the downwards weight force
Once air resistance equals weight, there is no longer any resultant force
Therefore, the skydiver’s acceleration is zero - they now travel at a constant speed
This speed is called their terminal velocity
What is Newton’s First Law of Motion?
> ‘If the resultant force of a stationery object = 0, the object will remain stationery.
If the resultant force of a moving object is 0 then it will carry on moving at the same velocity’.
What is Newton’s second law of motion?
‘The larger the resultant force acting on an object, the more the object accelerates’.
What is the formula to workout force?
F=MA
Force= Mass X Acceleration
What is Inertia?
> The tendency for the motion of an object to remain unchanged.
What is Newton’s Third law of motion?
‘When two objects, the forces they exert on each other are equal and opposite’.
Memorise Required Practical
Acceleration one…..
What is the stopping distances?
> Minimum distance required to stop a vehicle in an emergency.
What is the formula to workout stopping distance?
Stopping Distance= Thinking + Braking Distance
What is the thinking distance?
> How far the car travels during the driver’s reaction time.
What is the Braking distance?
> The distance taken to stop under the breaking distance.
What are factors affecting thinking distance?
> Speed, the faster the further you’ll travel,
Reaction time which varies between people.
Tired, drunk, drugs , distractions
What are factors affecting Braking distance?
> Speed, faster it travels longer it takes to stop
Weather or road surface
The condition of the tyres
The condition of brakes.
Explain what happened when you push the brakes.
> When the brake activates it presses against the wheel
Force of friction now acts between the break
Kinetic energy is converted in thermal energy, so the temperature of the brakes increases.
At the same time car slows down as it loses kinetic energy
the greater the speed the greater the braking force.
What is the formula for momentum?
Momentum=Mass X Velocity
(Kg m/s) = M x m/s
What is the conservation of momentum?
> In a closed system, the total momentum before an event is equal to the total momentum after an event,
So momentum is conserved.
