Answers:
a) 
b) 
Explanation:
a) The centripetal acceleration
of an object moving in a uniform circular motion is given by the following equation:
Where:
is the angular velocity of the ball
is the radius of the circular motion, which is equal to the length of the string
Then:
This is the centripetal acceleration of the ball
b) On the other hand, in this circular motion there is a force (centripetal force
) that is directed towards the center and is equal to the tension (
) in the string:

Where
is the mass of the ball
Hence:

This is the tension in the string
Answer:
v = 5.166 10² m / s
Explanation:
We can solve this exercise using the kinematics equations
v = v₀ + at
as the bullet starts from rest its initial velocity is zero
v = a t
let's calculate
v = 6.3 10⁵ 8.2 10⁻⁴
v = 5.166 10² m / s
A decagram is 1000 times bigger than a centigram
Part a
Answer: NO
We need to calculate the distance traveled once the brakes are applied. Then we would compare the distance traveled and distance of the barrier.
Using the second equation of motion:

where s is the distance traveled, u is the initial velocity, t is the time taken and a is the acceleration.
It is given that, u=86.0 km/h=23.9 m/s, t=0.75 s, 

Since there is sufficient distance between position where car would stop and the barrier, the car would not hit it.
Part b
Answer: 29.6 m/s
The maximum distance that car can travel is 
The acceleration is same, 
The final velocity, v=0
Using the third equation of motion, we can find the maximum initial velocity for car to not hit the barrier:

Hence, the maximum speed at which car can travel and not hit the barrier is 29.6 m/s.
Oil leakage in aquatic areas. (fish)
Burning fuel. (Air/global warming)
Toxic waste burried in dirt (living Creatures)
Lights/Electricity (destroyes Birds migration)
Noise (migration on dolphines and other sea mammals)