For which of the following motions of an object must the acceleration always be zero?
I. Any motion in a straight line
II. Any free fall motion
III. Any motion in a circle
it can be more than one :P
It is not guaranteed to be any of them, thus it is E.
To determine which motions of an object must have an acceleration of zero, let's analyze each option provided:
I. Any motion in a straight line:
In this case, if an object is moving in a straight line at a constant speed, then the acceleration will be zero. This is because acceleration is the rate of change of velocity, and if the velocity is constant, there is no change, hence zero acceleration.
II. Any free fall motion:
In free fall motion, an object is falling under the influence of gravity alone, with no other forces acting upon it. It is important to note that the acceleration due to gravity is constant near the Earth's surface. Therefore, during free fall, the acceleration will not be zero but will be equal to the acceleration due to gravity (approximately 9.8 m/s²).
III. Any motion in a circle:
When an object moves in a circle, it undergoes constant change in direction, which requires a force towards the center of the circle. This force is known as the centripetal force. Since acceleration is the rate of change of velocity, and velocity is a vector quantity that includes both speed and direction, any motion in a circle will have a non-zero acceleration value.
Based on the explanation above, the only motion listed where the acceleration will always be zero is option I: Any motion in a straight line.
The acceleration will always be zero for the following motions:
I. Any motion in a straight line
III. Any motion in a circle