A truck A of mass 2000 kg is initially at rest. It is hit by another truck B of mass 1200 kg moving at 3 m/s. If electronic equipment of mass 300 kg is loaded onto truck B before the collision, what i

The weight of truck A is a force exerted by Earth on truck A, directed downwards. According to Newton's Third Law, the reaction force is exerted by truck A on Earth.

The mass of truck A is $m_A = 2000 \text{ kg}$. The acceleration due to gravity is $g = 9.8 \text{ m} \cdot \text{s}^{-2}$.

The reaction force to the weight of truck A is a force of $19600 \text{ N}$ exerted by truck A on Earth, directed upwards.
The magnitude is $19600 \text{ N}$ and the direction is upwards.

Mass of truck A: $m_A = 2000 \text{ kg}$
Initial velocity of truck A: $u_A = 3 \text{ m} \cdot \text{s}^{-1}$ (westwards)
Mass of truck B: $m_B = 1200 \text{ kg}$
Mass of electronic equipment: $m_{eq} = 300 \text{ kg}$
Total mass of truck B (including equipment): $M_B = m_B + m_{eq} = 1200 \text{ kg} + 300 \text{ kg} = 1500 \text{ kg}$
Initial velocity of truck B: $u_B = 0 \text{ m} \cdot \text{s}^{-1}$ (stationary)
After the collision, the two trucks combine, meaning it is an inelastic collision. Let the final velocity of the combined system be $v_f$.

The total momentum before the collision equals the total momentum after the collision.

Let westwards be the positive direction.

The final velocity of the combined trucks (which includes truck B) is $1.71 \text{ m} \cdot \text{s}^{-1}$ westwards.

Mass of truck B (with equipment): $M_B = 1500 \text{ kg}$
Initial velocity of truck B: $u_B = 0 \text{ m} \cdot \text{s}^{-1}$
Final velocity of truck B (from 6.2): $v_f = \frac{12}{7} \text{ m} \cdot \text{s}^{-1}$
Duration of collision: $\Delta t = 0.5 \text{ s}$

The impulse exerted on truck B is equal to the change in momentum of truck B.