SP1. A railroad engine moves forward along a straight section of track for a distance of 70 m due west at a constant speed of 5 m/s . It then reverses its direction and travels 32 m due east at a constant speed of 4 m/s . The time required for this deceleration and reversal is very short due to the small speeds involved. a. What is the time required for the entire process? b. Sketch a graph of average speed versus time for this process . Show the deceleration and acceleration upon reversal as occurring over a very short time interval . c. Using negative values of velocity to represent reversed motion, sketch a graph of velocity versus time for the engine ( see fig. 2.15 ). d. Sketch a graph of acceleration versus time for the engine (see fig . 2.16).

    m₁v₁ + m₂v₂ = (m₁ + m₂)vmomentum is conserved.the left-hand side of the equation represents the momentum in the system before the collision.the right-hand side represents the momentum in the system after the collisionm₁ and v₁ represents the mass and the velocity of the physics blockm₂ and v₂ represents the mass and velocity of the ball of puttyv represents the final velocity of the combined mass.the question states the two masses stick together. they combined mass has its own velocity with the body mass the sum of the two objects' massestheir combined momentum is (m₁ + m₂)vto find the magitude of (m₁ + m₂)v, we need to add the vectors on the left-hand side of the equation: m₁v₁ + m₂v₂.note the diagram. i have positioned the vectors in accordance with their directions.the magnitude of the resultant can be calculated using the pythagorean theorem since this is a right triangle situation (north and west are perpendicular)|(m₁ + m₂)v| =  √[ (m₁v₁)² + (m₂v₂)² ]|(m₁ + m₂)v| =  √[ (1.5kg·8.0m/s)² + (0.40kg·20m/s)² ]|(m₁ + m₂)v| =  14.4 kg m/sfor two significant figures (assuming that 20m/s is two), this rounds to 14 kg m/s

Lexy is correct because angle r is between the incident wave,  n  = 0, and a diffracted wave.

B. that is the answer