Answer:
over harvesting, pollution, introduction of invasive species such as new predators and food competitors
Explanation:
The main cause of mass extinction is Humans cause extinction of a species through overharvesting. The second main cause is pollution ., introduction of invasive species such as new predators and food competitors, habitat destruction, overhunting and other influences. Another very important cause of mass extinction is the unsustainable human population growth.
The five mass extinction events are
Ordovician Mass Extinction
Devonian Mass Extinction
Permian Mass Extinction
Triassic -Jurassic Mass Extinction
and Cretaceous -Tertiary (or the K-T) Mass Extinction.
The position of the centre of gravity of an object affects its stability. The lower the centre of gravity (G) is, the more stable the object. The higher it is the more likely the object is to topple over if it is pushed. Racing cars have really low centres of gravity so that they can corner rapidly without turning over.
Increasing the area of the base will also increase the stability of an object, the bigger the area the more stable the object. Rugby players will stand with their feet well apart if they are standing and expect to be tackled.
<u>Answer:</u>
Cannonball will be in flight before it hits the ground for 2.02 seconds
<u>Explanation:</u>
Initial height from ground = 20 meter.
We have equation of motion , 
, s is the displacement, u is the initial velocity, a is the acceleration and t is the time.
In this the velocity of body in vertical direction = 0 m/s, acceleration = 9.8 
, we need to calculate time when s = 20 meter.
Substituting
So it will take 2.02 seconds to reach ground.
