which one is angle will give the longest range ? 30 degrees ? 45 degrees ? 60 degrees ?

It depends on the initial height. However, if initial height = 0, then 45 degrees will give you the longest distance.

range= VcosTheta*time

timeinair:
hf=ho+VisinTheta*t-1/2 g t^2

or 1/2 gt^2-ViSinTheta*t+(hf-ho)=0
and you solve for t. Clearly, the hf-ho term at first glance seems to matter. Lets check it.

using the quadratic equation.

t= (ViSinTheta+-sqrt(Vi^2Sin^2Theta-2g(hf-ho))/g

taking the + sqrt solution, put that into the horizontal equation..

range=VicosTheta(ViSinTheta/g +sqrt(Vi^2sin^2theta-2(hf-ho)/g)

now,with the assistance of calculus, maximizing range (drange/dtheta =0

0=Vi^2 [sin^2theta/g - cos^2theta/g)+1/2 1/sqrt( ) *2sinthetacostheta)

and you solve for theta

and the solution is a lot of algebra, but what I want to point out, the factor (Hf-ho) is in that squareroot function in the denominator,so as Max points out, it matters the difference in height.

To determine the angle that will give the longest range, we can use principles of projectile motion. In this case, we are assuming that the projectile is being launched at the same initial velocity from the same point.

The range of a projectile can be calculated using the following formula:

Range = (v^2 * sin(2θ)) / g

Where:
- v is the initial velocity of the projectile
- θ is the angle of launch
- g is the acceleration due to gravity (approximately equal to 9.8 m/s^2)

To find the angle that gives the longest range, we can compare the range values for each given angle.

Let's calculate the ranges for each angle:
1. For 30 degrees:
Range(30°) = (v^2 * sin(2*30°)) / g

2. For 45 degrees:
Range(45°) = (v^2 * sin(2*45°)) / g

3. For 60 degrees:
Range(60°) = (v^2 * sin(2*60°)) / g

Keep in mind that the initial velocity should be the same for all cases in order to accurately compare the ranges.

After calculating the ranges for each angle, compare the values. The angle that gives the longest range will have the highest value.

To determine which angle will give the longest range, we need to understand the concept of projectile motion. When an object is launched into the air at an angle, it follows a curved path known as a projectile trajectory. The range refers to the horizontal distance covered by the projectile.

The range of a projectile is maximized when it is launched at an angle of 45 degrees. This particular angle provides the optimum balance between vertical and horizontal components of motion. At this angle, the initial velocity is divided equally between the vertical and horizontal directions, resulting in the longest possible range.

To understand this concept intuitively, think about launching a projectile at a very low angle (e.g., 10 degrees). In this case, most of the initial velocity is directed vertically, leading to a steep trajectory and a shorter range. On the other hand, launching the projectile at a higher angle (e.g., 60 degrees) allocates more of the initial velocity horizontally, reducing the vertical component and causing the projectile to spend more time in the air without covering significant horizontal distance.

Therefore, based on this information, the angle of 45 degrees is the best choice for achieving the longest range when launching a projectile.