Question

Example 9.7 A girl of mass 40 kg jumps
with a horizontal velocity of 5 msonto
a stationary cart with frictionless
wheels. The mass of the cart is 3 kg.
What is her velocity as the cart starts
moving? Assume that there is no
external unbalanced force working in
the horizontal direction.​

Answer 1

Explanation:

Given : M

girl

=40 kg u

girl

=5 m/s M

cart

=3 kg

Initial velocity of cart u

cart

=0

Let the final velocity of cart be V.

Applying conservation of linear momentum : P

i

=P

f

Or M

girl

u

girl

+M

cart

u

cart

=(M

girl

+M

cart

)V

Or 40×5+3×0=(40+3)V

⟹ V=

43

200

m/s

Answer 2

Answer:

Mass of the girl = 40 kg

Mass of the cart = 3 kg

Velocity of the girl = 5 m/s

Velocity of the cart = 0 m/s

To Find :-

Velocity as the cart starts moving.

Solution :-

Firstly let's find the Mounmentum of girl

[P = mv]

Here,

P = Mounmentum

M = Mass

V = Velocity

P = 40 × 5

Hence, Mounmentum of girl is 200 kg m/s .

Now,

Let's add the Mounmentum of girl and cart

200 + 0 = 200 kg m/s

Let's find total mass

Total mass = 40 + 3 = 43 kg

Velocity=Mounmentum/mass

V = P/M

Velocity = 200/43

Hence :-

Velocity of cart is when start moving is 4.65 m/s.

@ananya