Renewable resources are those natural resources which are filled again naturally such as sunlight,air and wind etc,these natural resources are persistenty available and their quantity is not usually affected by human consumption.

A projectile is any object that is given an initial velocity and then follows a path determined entirely by gravity.
There are following factors that affect projectile trajectory:
1.Angle of projection:Any object when projected at different angles covers different distances.When it is released at the angle of 30 degree,making a parabolic path ,it covers less ditance.When it is released at the angle of 45 degree ,it covers the maximum distance.So the distance covered by an object depend on the angle of release of projectile.
2.Initial velocity :The distance covered by an object depend on the initial velocity of the projectile.If the initial velocity is more the object cover maximum distance.On the other hand,if initial velocity is less, the object cover less distance.
3.Gravity:It is the force of attraction excerted by the earth towards uts centre on a body or an object.The greater the weight of an object ,the greater the influence of gravity upon it.

Differences between walking and running:
1. There is a double support phase during running whereas,there is a double support phase during walking.
2. In running the swing phase is longer whereas, stance phase is longer in walking.
3. In running, there is floating phase but it is absent in walking.
4.The linear and angular velocity of lower extremity is faster in running but slower in walking.
5. In running the required range of motion is greater whereas it is required less in walking.
Mechanical analysis of running;
1. Stance phase:The stance phase is that phase is which the foot is in contact with the ground. This phase can be divided into the four stages which are described below:
a) Initial contact stage: This stage begins at the moment when both feet are off the ground.Suppose the left leg remains in the front and  about to touch the ground.The moment, when the foot touches the ground is called as initial contact stage.
b) Braking or absorption stage: When the left foot makes the initial contact to the ground in your front,your body starts performing a controlled landing.The left knee and ankle flex and the left foot rolls to absorb forces.It is called braking or absorption stage.
c) Midstance stage: The braking or absorption stage continues until the left leg is directly under the hip  taking maximum load as the boby weight passes over it.
d) Propulasive stage: Propulsive stage occurs when the supporting leg or left foot leaves the ground and propel your body in forward direction.Propulsion is achieved by your left ankle, knee and hip all extending to push the body up and forward using the elastic energy stored during the absorption phase.
2. Swing phase: Swing phase is initiated with toe off of left foot and ends with intial contact stage with right foot. The swing phase is longer in running in comparison to stance phase.

The angle of 45 degree is the best angle for achieving maximum distance.