Question

A girl of mass 50kg jumps with a horizontal velocity of 10m/s onto a stationary cart with frictionless wheels. The mass of the cart is 5kg. What is her velocity as the cart starts moving?

Answer 1

Answer:mass of girl- 50 kg(m1), initial velocity of girl- 10m/s(u1), final velocity- ?mass of cart- 5kg(m2), intial velocity of cart- 0m/s (u2) (since it is stationary)

Now, to find the final velocity of girl:-

Initial momentum:-

p= m1u1+ m2u2p

= 50×10+ 5×0

= 500+ 0

= 500kg m/s

Final momentum:-

p= (m1+m2) v

= (50+5)v

= 55v kg m/s

According to conservation of momentum:-

500 = 55v

500÷55 = v

9.09 = v

Therefore, 9.09m/s is the final velocity of girl.

Answer 2

$\large\sf\green{Total\:momentum=40×5+3×0}$

$\longrightarrow$$\large\sf\green{200kg\:m/s}$

$\large\sf\pink{Total\:momentum\:after\:interaction=}$

$\longrightarrow$$\large\sf\pink{(40+3)kg×vm/s}$

$\longrightarrow$$\large\sf\pink{43vkg\:m/s}$

$\large\sf\purple{43v=200}$

$\large\sf\purple{v=\frac{200}{43}}$

$\large\sf\purple{v=4.65m/s}$