Ryder has been visiting his favorite park for ten years. Recently, he noticed that the large boulder in the center of the park has gotten smaller and smoother in some places. Why has the boulder changed? A. Wind and water have weathered the boulder, wearing away at its surface. B. The weight of the boulder has caused its rock particles to compress. C. The rock particles in the boulder have cemented into thinner layers. D. The heat of the Sun evaporated out the water, causing the boulder to shrink.

um i think it might be a car?

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied