Question

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Answer 1

Let us consider initial velocity of boy to be b and of cart to be c. Masses are mb and mc respectively. A 20% increase in the velocity of cart means if it was 1 before, it is 1.2 now so we get final velocity as 1.2c. Now according to question, the boy is climbing on the cart so final velocities of cart and boy should be the same i.e. 1.2c . Always remember in such cases to consider the boy and cart to be an isolated system where we can apply conservation of linear momentum. Refer to picture below for calculations. According to me the answer is B)4

Hope it helps

Answer 2

Answer:

Answer in the attachment