# Question #fc978

##### 1 Answer

The height of the building: **45 m**.

The angle of contact:

#### Explanation:

**FULL QUESTION**

*A particle is projected horizontally from the top of a building in a velocity of* *It hits the ground 45m away from the bottom of the building.*

*What is the height of the building?**What is the angle it creates with the horizontal when it hits the ground?*

Like with any projectile motion problem, the basic idea is that your particle's trajectory can be broken down into a **vertical** and a **horizontal** component.

The same can be said for the particle's *initial velocity*. However, when you launch a particle *horizontally*, the nagle it makes with the horizontal is of course

The vertical component of the initial speed will be **zero**.

So, **horizontally**, the movement of the particle is not affected by any forces, which means that you can write

Plug your values into this equation to get the time of flight

The particle is in flight for only 3 seconds.

**Vertically**, the gravitational acceleration will affect the movement of the particle. This implies that *vertical component* of its velocity will **increase** as the particle descends from the building.

Taking into account that the vertical displacement is **negative**, you can write

To get the angle of contact with the ground, you need to determine the vertical component of its final velocity.

Use the equation

The horizontal component of the velocity is constant,

To get

Therefore,