Solve Freefall Problem: Find Speed of Stone Thrown Upward

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In summary, the homework question is asking for the initial speed of a stone that was thrown straight upward and reached a height of 20.0m. The necessary equations to solve this problem are the kinematic equations, specifically v=u+at, s=ut+1/2at^2, and v^2=u^2+2as. It is also helpful to use the symmetry in the rise and fall of an object, and in this case, the equation v^2=2gh can be used to calculate the initial speed.
  • #1
culexor
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I need help getting the base equations for a situation like this so I can complete all of the other problems on the page. Thanks ahead of time.

Homework Statement


A stone is thrown straight upward and it rises to a height of 20.0m. With what speed was it thrown?


Homework Equations


This is what I need.


The Attempt at a Solution


Answer: 19.8 m/s (given, the equations are what I need)
 
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  • #2
g is constant so the kinematic equations apply

those are v=u+at;s=ut+1/2at^2;v^2=u^2+2as

Where v=final speed,u=initial speed,a=acceleration,s=displacement
 
  • #3
It's always very useful and time saving to use the symmetry in the rise and fall of an object. This means that in this case we have to calculate the speed after a fall of 20 m from rest. The eqn v^2 = 2gh gives it directly.
 

Related to Solve Freefall Problem: Find Speed of Stone Thrown Upward

What is freefall?

Freefall is the motion of an object under the influence of gravity alone, without any other forces acting on it. In other words, it is the motion of an object where the only force acting on it is gravity and there is no air resistance.

What is the equation for freefall?

The equation for freefall is v = v0 + at, where v is the final velocity, v0 is the initial velocity, a is the acceleration due to gravity, and t is the time.

How do you solve for the speed of a stone thrown upward?

To solve for the speed of a stone thrown upward, you can use the equation v = v0 + at. First, determine the initial velocity, which is the speed at which the stone is thrown. Then, use the acceleration due to gravity, which is approximately 9.8 m/s2 on Earth. Finally, use the time the stone is in the air to calculate the final velocity.

What is the initial velocity of a stone thrown upward?

The initial velocity of a stone thrown upward is the speed at which the stone is thrown. This can vary depending on the person throwing the stone, but it is generally between 10-20 m/s.

How does air resistance affect the speed of a stone thrown upward?

Air resistance can affect the speed of a stone thrown upward by slowing it down. This is because as the stone moves through the air, it experiences a force in the opposite direction of its motion due to air resistance. This force increases as the speed of the stone increases, which can cause the stone to slow down and have a lower final velocity than if it were in a vacuum.

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