Question

Мальчик массой 50 кг бежит со скоростью 5м/с, догоняет стоящую тележку массой 15кг и вскакивает на нее. С какой скоростью станет двигаться тележка с мальчиком после этого? Заранее спасибо

Answer 1

(100*2+50*5)/150=450/150=3

Answer 2

Calculation of Final Velocity

To determine the final velocity of the boy and the cart after he jumps onto it, we can use the principle of conservation of momentum. According to this principle, the total momentum before the boy jumps onto the cart is equal to the total momentum after the jump.

The momentum of an object is calculated by multiplying its mass by its velocity. Therefore, the momentum of the boy before the jump is given by:

Momentum of the boy before the jump = mass of the boy × velocity of the boy

Given that the mass of the boy is 50 kg and his velocity is 5 m/s, we can calculate his momentum before the jump.

Momentum of the boy before the jump = 50 kg × 5 m/s = 250 kg·m/s The momentum of the cart before the jump is given by:

Momentum of the cart before the jump = mass of the cart × velocity of the cart

Given that the mass of the cart is 15 kg and it is initially stationary (velocity = 0 m/s), the momentum of the cart before the jump is 0 kg·m/s.

Since momentum is conserved, the total momentum after the jump is equal to the total momentum before the jump. Therefore, the momentum of the boy and the cart after the jump is also 250 kg·m/s.

Let's assume the final velocity of the boy and the cart after the jump is v. The momentum of the boy and the cart after the jump can be calculated as follows:

Momentum of the boy and the cart after the jump = (mass of the boy + mass of the cart) × final velocity

Substituting the known values, we have:

250 kg·m/s = (50 kg + 15 kg) × v

Simplifying the equation:

250 kg·m/s = 65 kg × v

Solving for v:

v = 250 kg·m/s / 65 kg ≈ 3.85 m/s

Therefore, the final velocity of the boy and the cart after he jumps onto it is approximately 3.85 m/s.