# Optimal Angle for a Fireman Shooting Water from a 20m High Roof

• Fusilli_Jerry89
In summary, the fireman should aim the hose at an angle of 45 degrees above the horizontal in order to hit the other roof. This can be calculated by splitting the trajectory into horizontal and vertical components and using kinematic equations to solve for the launch angle. The initial horizontal velocity is 12m/s and the initial vertical velocity is 0m/s. The change in vertical displacement is 0m and the change in horizontal displacement is 21m. The acceleration in the vertical plane is -9.8m/s^2. By finding the time through vertical resolution and using trigonometric functions, the launch angle can be determined to be 45 degrees.
Fusilli_Jerry89
A fireman shoots water out of a hose at 12m/s. he is standing on a 20m high roof and is aiming for the top of another roof at the same height, but it is 21 m away. What angle should the fireman aim the hose above the horizontal in order to hit the other roof?

i set up a chart but have no idea what to do now:
x y
vi " '
vf " -'
a 0 -9.8
d 21 0
t

You need to split up the trajectory into horizontal and vertical components, start by writing down the following;

• Initial Horizontal Velocity*
• Initial Vertical Velocity*
• Change in Vertical Displacement
• Change in Horizontal Displacement
• Acceleration in the vertical plane

Note that (*) will be trigonometric functions of the launch angle. Once you have done this, apply kinematic equations to each component independently.

In questions about projectiles, it is quite often, like in this case that you will need to find the time by resolving it vertically.

## 1. What is the optimal angle for a fireman to shoot water from a 20m high roof?

The optimal angle for a fireman to shoot water from a 20m high roof is 45 degrees. This angle allows for the water to travel the furthest distance while also maintaining enough force to effectively put out the fire.

## 2. Why is the optimal angle for a fireman to shoot water from a 20m high roof 45 degrees?

The optimal angle of 45 degrees is determined by the laws of physics, specifically the projectile motion equation. This angle allows for the maximum range and height of the water while also taking into account air resistance and gravity.

## 3. Is the optimal angle for a fireman to shoot water from a 20m high roof the same for all types of fires?

No, the optimal angle may vary depending on the type of fire and the location of the fire. For example, a fire on a lower level may require a different angle than a fire on a higher level.

## 4. Can changing the angle of the water stream affect its effectiveness in putting out a fire?

Yes, changing the angle of the water stream can affect its effectiveness in putting out a fire. Angling the water too high or too low can result in the water missing the fire or losing too much force before reaching the fire.

## 5. Are there any other factors besides angle that can affect the effectiveness of a fireman shooting water from a 20m high roof?

Yes, there are other factors that can affect the effectiveness of a fireman shooting water from a 20m high roof. These include wind speed and direction, the volume and pressure of the water, and the type of nozzle being used.

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