Final answer:
The particle's position relative to the origin at t=7 seconds is -14 meters.
Step-by-step explanation:
Given that the particle starts from rest at a position of +10 meters from the origin, and accelerates at a constant rate of -2m/s² in the negative direction, we can calculate its position at t=7 seconds.
First, we need to find the velocity of the particle at t=4 seconds. Since it starts from rest and accelerates at a rate of -2m/s², we can use the equation v = u + at, where u is the initial velocity, a is the acceleration, and t is the time. Plugging in the values, we get v = 0 + (-2)(4) = -8 m/s.
Next, we need to find the displacement of the particle from t=4 seconds to t=7 seconds. Since the particle travels at a constant velocity after t=4 seconds, its displacement is equal to the product of its velocity and the time interval. So, the displacement is (-8)(7-4) = -24 meters.
Finally, we add the displacement to the initial position (+10 meters) to find the particle's position relative to the origin at t=7 seconds. Therefore, the particle's position relative to the origin at t=7 seconds is -24 + 10 = -14 meters.