Calculating Final Speed of a Thrown Object with Changing Momentum

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A 60kg person throws two 10kg blocks at 5m/s, and the calculation of her final speed after each throw is debated. Initially, the speed after the first throw is calculated as 5/7 m/s, leading to a final speed of 5/3 m/s after the second throw. However, the provided answer is 1.55 m/s, which is lower than the speed gained if both blocks were thrown simultaneously. The discrepancy arises from the changing speed of the person affecting the velocity of the thrown blocks relative to the ground. Understanding the relationship between the person's speed and the blocks' speed is crucial for accurate calculations.
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A 60kg person is holding two 10kg blocks and she throws them one at a time at 5m/s.
What is her final speed?

What I get is,
after she throws the first rock 0=70v-50 so her speed is 5/7 m/s,
and after she throws the second 5/7 *70=60v-50 so her final speed is 5/3 m/s (1.67 m/s)

But the answer says 1.55 m/s which is less than the speed she would gain if she throws the two rocks simultaneously (5/3 m/s).
What am I doing wrong?
 
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The speed of each thrown block is 5 m/s with respect to the person. As the person's speed changes, so does the speed of a thrown block with respect to the ground.
 
Doc Al said:
The speed of each thrown block is 5 m/s with respect to the person. As the person's speed changes, so does the speed of a thrown block with respect to the ground.

Ofcourse... thank you!
 

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