# Calculating the Velocity of a Rock Thrown from a Building Roof

• magasiki
In summary, to calculate the magnitude of the velocity of a rock just before it strikes the ground when thrown from the roof of a building with a velocity v_0 at an angle of alpha_0 from the horizontal and a height h, you can use the equation V=V_0 + at. It is important to note that other kinematic equations may also be used and the answer should be expressed in appropriate constants. Additionally, the fundamental equation of motion valid for all classical physics problems is v = x/t.

#### magasiki

A rock is thrown from the roof of a building with a velocity v_0 at an angle of alpha_0 from the horizontal. The building has height h. You can ignore air resistance.

Calculate the magnitude of the velocity of the rock just before it strikes the ground.

V=V_0 + at
X=V_0t + 1/2at^2

## The Attempt at a Solution

v_0(sin(alpha_0))-2(v_0)
The catch is that when i put the answer into the system, it told me that v_o and alpha_0 are not part of the answer. Any help is appreciated.

Well, there are other kinematic equations, and I presume you would need to use the height, so look into the equations involving height. Do you know what constants the answer should be expressed in?

Or, don't bother about sub-equations at all!

What is the FUNDAMENTAL equation of motion valid for ALL CLASSICAL PHYSICS PROBLEMS?

I also need help with this... is the equation you're talking about v = x/t?

## 1. What is the potential energy of a rock thrown from a roof?

The potential energy of a rock thrown from a roof depends on the mass of the rock, the height of the roof, and the gravitational acceleration (9.8 m/s^2). The formula for potential energy is P.E. = mgh, where m is the mass in kilograms, g is the gravitational acceleration, and h is the height in meters. Therefore, the potential energy will increase as the mass and height of the rock increase.

## 2. How does air resistance affect the trajectory of a rock thrown from a roof?

Air resistance, also known as drag, can affect the trajectory of a rock thrown from a roof. As the rock moves through the air, it experiences a force in the opposite direction of its motion due to air resistance. This force can cause the rock to slow down and alter its trajectory, making it fall at a steeper angle than if there was no air resistance.

## 3. Can a rock thrown from a roof reach escape velocity?

No, a rock thrown from a roof cannot reach escape velocity. Escape velocity is the minimum speed required for an object to escape the gravitational pull of a planet. Since the gravitational pull of the Earth is much stronger than the force with which a person can throw a rock, the rock will not be able to reach escape velocity.

## 4. How does the shape of the rock affect its trajectory when thrown from a roof?

The shape of the rock can affect its trajectory when thrown from a roof. A more aerodynamic shape, such as a streamlined rock, will experience less air resistance and therefore travel further than a less aerodynamic shape, such as a jagged rock. This is because the streamlined rock will have a more efficient path through the air, reducing the effects of air resistance.

## 5. Why does a rock thrown from a roof fall to the ground instead of continuing to rise?

A rock thrown from a roof falls to the ground due to the force of gravity. Gravity is the force that attracts objects towards each other, and on Earth, it pulls objects towards the center of the planet. When a rock is thrown from a roof, the force of gravity acts on it, pulling it towards the ground. As the rock's upward motion slows down, the force of gravity becomes stronger, causing it to eventually fall to the ground.