Motion, Scalar and Vector

Motion, Kinematics and Dynamic motion. Scalar and Vector.

1. Motion Jerome a. bigael Leyte progressive high school

2. In July 1969, Neil Armstrong (1930-2012) said, “One step of man, one giant leap for mankind.” From that time, great leaps and progress in science and technology were made. Wireless communication , genetic engineering, and space explorations are just some of some mankind’s achievement.

3. Armstrong was able to leap on the surface of the moon at a height which he could not have reached on Earth because of gravity. As you know, the gravitational force on the moon is less compared to that on Earth.

4. Definition of Motion Reference points are very important in describing the motion of objects. It is a fixed  point  and does not move so that the position of an object is described by the coordinate with respect to the  reference point . If you are standing still, can you say you are in motion ? The answer depend on the reference point . Video

5. If you ask that question to a classmate who is in the same room, he or she might tell you that you are not moving . But if you ask an observer from a satellite orbiting Earth , he or she might say “yes you are moving”. Since Earth is rotating about it’s axis, the observer from an orbiting satellite will tell you that you are moving . Thus motion is a change in position with respect to a reference point and time .

6. The study of motion can be divided into 2 Kinematics and Dynamics Kinematics = describes motion in terms of displacement. Dynamics = relates force and motion. Translation is the term used in physics for motion in a straight line.

7. In our study of translation, we shall consider the origin of the Cartesian coordinate as start of motion. Position, velocity, and acceleration to the right of the origin are considered positive . On the other hand, position, velocity, and acceleration to the left of the origin shall be considered negative . *on the next section we will consider motion along the horizontal axis.

8. Distance versus Displacement Quantities that are used to describe motion of an object can either be scalar or vector . Scalar quantities are those that can be described completely by their magnitudes and appropriate units .

9. What is a magnitude? the meaning of magnitude is 'size' or 'quantity' .

10. Vector quantity are those that are completely described by their magnitudes , appropriate units , and directions .

11. A distinction has to be made between distance and displacement. Distance is scalar . Distance d travelled by an object is the length of the path taken by an object from its initial to its final position.

12. Displacement d is a vector with direction pointing from the initial to the final position and magnitude or length equal to the straight line distance from the initial to final position.

13. Quiz 1. A physical quantity which has direction as well as magnitude is known as a: force vector scalar weight

14. 2. Which of the following is not a scalar quantity? (a) velocity ( b) potential energy (c) work ( d) kinetic energy

15. 3 . Which of the following is not a vector quantity? (a) displacement ( b) density (c) velocity ( d) acceleration

16. 4. Which of the following statements is false? ( a) Scalar quantities have size or magnitude only (b) Vector quantities have both magnitude and direction (c) Mass, length and time are all scalar quantities (d) Distance, velocity and acceleration are all vector quantities

17. 5. Identify the following quantities as scalar or vector: the mass of an object, the number of leaves on a tree, wind velocity . A.  Vector , scalar, scalar B.  Vector , scalar, vector C.  Scalar , scalar, vector D.  Scalar , vector, vector

18. Answer key: 1.b 2.a 3.b 4.d 5 . C