How to Determine the Speed of Ball B When Two Balls Pass Each Other?

In summary, two balls, A and B, are released at the same time from different heights, h1 and h2 respectively, and pass each other at a height of h3. The goal is to determine the speed at which ball B was thrown upward. To solve this, we can use the three equations of motion, as the acceleration is constant. By finding the time at which they meet, using the equation for ball A, we can then plug that into the equation for ball B to solve for its speed.
  • #1
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Homework Statement


Ball A is released from rest at height h1 at the same time that a
second ball B is thrown upward from a distance h2 above the
ground. If the balls pass one another at a height h3 determine the
speed at which ball B was thrown upward.
Given:
h1 = 40 ft
h2 = 5 ft
h3 = 20 ft
g =32.2 ft/sc2

Homework Equations


the equation to be used are the three equations of motion, as the acceleration is constant.

The Attempt at a Solution


I couldn't attempt the solution becuase I am stuck a every equation as therer are many unknowns for ball B. WHat I can not find out yet is the relation between ball A and Ball B when they pass each other. There has to be property common in both at that time so that I can solve for B then. But again, after a lot of thinking I don't get how to do it still. Couldn't make any logic. The distance traveled is already given. Time taken and velocity will not be the same. What then?
 
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  • #2


The "properties" that will be the same are the height and the time. They will be at the same height at the same time. But the problem is actually much simpler. You know where they meet so you can find the time from the equation for ball A and then plug into the equation for ball B.
By equations here I mean equations of motion (height versus time).
 
  • #3


My confusion is that why will they take same time to meet each other? Like ball A can be at the meeting ponit in 5 secs while ball B can be there in 3 secs. I mean isn't it supposed to be dependent on their speeds ? How can we say here that they will meet each other at same time?
 

FAQ: How to Determine the Speed of Ball B When Two Balls Pass Each Other?

What is the "Three equations of motion problem"?

The "Three equations of motion problem" is a physics concept that involves using three equations - displacement, velocity, and acceleration - to solve for an unknown variable in a motion problem. These equations are based on Newton's laws of motion and can be used to describe the motion of an object in one dimension.

What are the three equations of motion?

The three equations of motion are:

  • Displacement equation: d = v0t + 1/2at2
  • Velocity equation: v = v0 + at
  • Acceleration equation: v2 = v02 + 2ad

These equations can be used to solve for an unknown variable, such as displacement, velocity, or acceleration, in a motion problem.

How do I identify which equation to use in a three equations of motion problem?

To identify which equation to use, you need to know what information is given in the problem. If you are given the initial velocity (v0), final velocity (v), and time (t), you can use the velocity equation. If you are given the initial velocity (v0), acceleration (a), and displacement (d), you can use the displacement equation. If you are given the initial velocity (v0), final velocity (v), and displacement (d), you can use the acceleration equation.

Can the three equations of motion be used in any motion problem?

No, the three equations of motion can only be used in motion problems where the acceleration is constant. This means that the velocity and acceleration do not change throughout the motion. If the acceleration is not constant, other equations and concepts, such as calculus, may be needed to solve the problem.

How do I solve a three equations of motion problem?

To solve a three equations of motion problem, you need to follow these steps:

  1. Identify the given information and what you are trying to solve for.
  2. Determine which equation to use based on the given information.
  3. Substitute the known values into the equation.
  4. Solve for the unknown variable using algebraic manipulation.
  5. Check your answer and make sure it makes sense in the context of the problem.

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