Answer the following questions for projectile motion on level ground assuming negligible air resistance (the initial angle being neither 0° nor 90° ): (a) is the velocity ever zero? (b) when is the velocity a minimum? a maximum? (c) can the velocity ever be the same as the initial velocity at a time other than at t = 0? (d) can the speed ever be the same as the initial speed at a time other than at t = 0?

(a) Is the velocity ever zero?

NO, it will never become zero

Explanation:

Since velocity is constant always along x direction as there is no acceleration in that direction so its velocity in x direction always remains same and net velocity is never zero during motion.

(b) When is the velocity a minimum? A maximum?

Velocity is minimum when it will reach the maximum height.

Velocity is maximum when it will reach the ground back or initial velocity is maximum

Explanation:

Since we know that y component of velocity will become zero at its maximum height

So here we can say that velocity is minimum when it will reach the top point of its path.

Since during its upward motion it is moving against gravity so here its vertical component of velocity will decrease with time

So maximum velocity is either initial velocity of the velocity when it will hit the ground again

(c) Can the velocity ever be the same as the initial velocity at a time other than at t = 0?

No, it will never equal to its initial velocity

Explanation:

It is never equal to initial velocity because here its direction of motion will change with time and since velocity is a vector quantity so here its direction never equal to initial velocity.

(d) Can the speed ever be the same as the initial speed at a time other than at t = 0?

Yes speed will be same when it will hit the ground again

Explanation:

Since we know by energy conservation law that here no frictional force acts on the object so energy will be same when it will hit the floor so here its speed will be equal to initial speed

28. evolution

29. environment, survive, offspring  

explanation: