Quiz 2: Kinematics: Description of Motion

Physics & Astronomy

The distance is the path length between initial and final positions whereas displacement shortest possible distance between initial and final positions. Assume a person moving from position A to position B by covering a path length of 5 km and return to same position A. In this, case the total path length travelled by the person is equal to 10 km and displacement is equal zero since initial and position of the person is same after trip. img there is a non-zero distance for zero displacement in a trip. The reverse situation is not possible because for every non-zero displacement there must be a distance that is equal to magnitude of the displacement since displacement is a vector. That is for non-zero displacement, the distance will not be zero. img there is no zero distance for non-zero displacement in a trip.

The linear distance between any two points indicates the magnitude of the displacement. If the two points are a half a lap apart on a circular path, then the linear distance between the two points indicates the diameter of the circle. img The diameter of the circular path of the car is equal to two times the radius of the circle. If the radius of the circular path of the car is R , then the diameter of the circular path of the car is, img Thus, the magnitude of the displacement of the car that travels half a lap along a circle is, img Substitute img for R. img Therefore, the magnitude of the displacement of the car that travels half a lap along a circle is img . The shortest distance from the initial point of the object to the final point of the object is defined as the displacement of the object. As the initial and final positions of the object coincide, the displacement of the object must be zero. If the car travels a full lap along the circle, the displacement of the car becomes zero because its initial and final positions coincide. Therefore, the displacement of the car when it travels a full lap along the circle will be zero.

A physical quantity which have only magnitude is called as scalar quantity and have both magnitude and direction is known as vector quantity. Here, magnitude is defined as the size or quantity, whereas the direction is referred as a vector, which is directed from one place to another. A vector has both magnitude and direction, the then option (c) is incorrect. A scalar quantity has only magnitude but no specified direction. Hence, the option (b) is also incorrect. Therefore, the correct answer is img .