- #1

rgtr

- 92

- 8

- Homework Statement
- q1

Bob is standing in the middle of a train moving at velocity v at constant velocity in the right direction. Bob throws 2 identical baseballs in opposite direction at the same speed at a constant velocity on the train. From Alice perceptive on the ground what is the velocity of the train?

q2

Now imagine I have 2 people running at a constant velocity towards each other in the same direction lets call the person on the left Alice and the person on the right Bob. Calculate from Alice's frame and Bob's frame the constant velocity?

q3

Now imagine I have 2 people running to the right in the same direction located at different locations let's call the person on the left Alice and the person on the right Bob. Calculate from Alice's frame and Bob's frame the constant velocity?

I am also assuming the earth is an inertial reference frame in all the questions

- Relevant Equations
- velocity addition vectors.

I kind of just made up the questions. I realize this is a basic question but my knowledge of physics is very limited.

v_left_ball = v_left_ball - v_train

v_right_ball = v_right_ball + v_train

To get the speed from Bob's frame I would use v_Bob = v_Bob + v_Alice

To get the speed from v_Alice = v_Bob + v_Alice

To get the speed from Bob's frame I would use v_Bob = v_Bob - v_Alice

To get the speed from Alice's frame I would use v_Alice = v_Alice - V_Bob

Assuming I am correct

Why are the people on the train and the ground different velocity addition laws?

I can't seem to find a discernible pattern.

Let's find the velocity_Left_ball for on the train.

IOW's

This is a shorter distance

v_train-------><-------v_left_ball

vs

**q1 answer**v_left_ball = v_left_ball - v_train

v_right_ball = v_right_ball + v_train

**q2 answer**To get the speed from Bob's frame I would use v_Bob = v_Bob + v_Alice

To get the speed from v_Alice = v_Bob + v_Alice

**q3 answer**To get the speed from Bob's frame I would use v_Bob = v_Bob - v_Alice

To get the speed from Alice's frame I would use v_Alice = v_Alice - V_Bob

Assuming I am correct

Why are the people on the train and the ground different velocity addition laws?

I can't seem to find a discernible pattern.

Let's find the velocity_Left_ball for on the train.

IOW's

**q1 answer**can be drawn as from Alice's frame.This is a shorter distance

v_train-------><-------v_left_ball

vs

**q1 answer**from Alice's frame I don't understand how to draw it or whyIn Alice's frame for the people on the ground running, I intuitively understand it but can't think of a vector diagram. Can someone help ?If I made any mistakes then please correct me.
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