Imagine Mr. Franklin sitting on a wheeled chair which can slide without friction on ground, with inevitable wad of chewing tabacco lodge in his mouth. Assuming he weighs 50 kg (including the chair), a

Question

Imagine Mr. Franklin sitting on a wheeled chair which can slide without friction on ground, with inevitable wad of chewing tabacco lodge in his mouth. Assuming he weighs 50 kg (including the chair), and is skilled enough in the art of spitting one cubic centimeter of spit, at 10 m/s with respect to ground each time he spits. How many times he would need to spit to attain a final speed of 1 cm/s ? Neglect variation in total mass of Mr. Franklin due to spitting. (Density of spit $= 1 g / cm^{3}$ )

Answer:

50

Solution:

Each spit carries momentum $1 \times 1000 = 1000$ g·cm/s

Recoil per spit: $v = \frac{1000}{50000} = \frac{1}{50}$ cm/s

To reach 1 cm/s: $n \times \frac{1}{50} = 1$

$n = 50$ times

TestHub · Accepted Answer

Each spit carries momentum 1 × 1000 = 1000 g·cm/s Recoil per spit: v = 50000 1000 ​ = 50 1 ​ cm/s To reach 1 cm/s: n × 50 1 ​ = 1 n = 50 times

Physics - NLM Question with Solution | TestHub

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