Which of the following statements is accurate?

a. if an object's velocity is changing, it's either experiencing acceleration or deceleration.
b. if an object's velocity decreases, then the object is accelerating.
c. if an object is said to be decelerating, its velocity must be increasing.
d. if an object's velocity remains constant, its acceleration must be increasing.

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

If you put a helium-filled balloon in the refrigerator, what will happen?

Ahot-air balloon is 11.0 m above the ground and rising at a speed of 7.00 m/s. a ball is thrown horizontally from the balloon basket at a speed of 9.00 m/s. ignore friction and air resistance and find the speed of the ball when it strikes the ground.