mechanics-newtons laws, terminal velocity,momentum Flashcards
What is newtons first law ?
If no resultant force acts upon a system it will remain at a constant velocity or remain at rest.
What is newtons second law ?
The rate of change of momentum(acceleration) is directly proportional to the force acting upon it .
Newtons second law is represented by the equation …
F=MA
What is newtons third law ?
When two objects interact they exert equal and opposite forces upon each other.
What is tension ?
A pulling force applied by a cable/rope.
Why does tension act away from the contact point ?
Because it is a pulling force.
What factors affect air resistance ?
Cross sectional area
shape of object
fluid density
velocity of object
What is terminal velocity ?
When drag force is equal to driving force.
Describe and explain motion of a skydiver before parachute is opened.
As soon as they leave the plane no air resistance because no vertical velocity.
Then they accelerate due to gravity until acceleration reaches 0 when drag=gravity.
Describe and explain motion of a skydiver after parachute is opened.
When parachute opens cross sectional area increases therefore air resistance increases therefore acceleration decreases
Velocity downwards increases due to acceleration by gravity until air resistance is equal to gravity where there is 0 acceleration.
What is momentum ?
MV=P
What are the 2 units for momentum ?
kgms-1
Ns
Is momentum scalar or vector ?
Vector.
What is the total momentum of a 2 identical balls with the mass of 2kg with one moving right at velocity of 4ms-1 and the other left 2ms-1
4kgms-1 right.
How can rate of change of momentum be calculated ?
dp/dt=F
How do you calculate momentum of a fluid flowing ?
Calculate volume of fluid produced per second
Calculate mass per second using D=M/V
length of prism of fluid per second is equal to velocity
Use P=MV to calculate momentum
What is the density of water ?
1000kgm-3
What is impulse equal to ?
change in momentum
force/dt
What is the area under a force time graph equal to ?
Impulse.
Explain how crumple zones in cars work ?
Crumple zones are parts of the car which deform during a car crash to increase time in contact with the body it collides with because Force exerted = change in momentum / time. therefore if time increases force decreases.
What is conservation of momentum ?
For a system of interacting objects the total momentum remains constant as long as no external force acts.
What is a elastic collision ?
A collision where there is no loss in kinetic energy.
What is a explosion ?
Where two objects which are initially at rest fly apart with equal and opposite momentum.
A cannon with the mass 500kg fired a cannonball with the mass of 20kg at the speed of 24ms-1. What is the speed of the recoil ?
-0.96ms
20x24=480
0=480-500x?
?=0.96
Negative due to it going in the opposite direction of the cannonball
