# Drawing velocity vectors for a body in uniform circular motion in Gravitation – Class 9 Science Experiment

**Chapter Name:** Gravitation

**Activity Name:**** **Drawing velocity vectors for a body in uniform circular motion **in **Gravitation

**Activity Description: **

In this experiment, we will study the motion of a wooden block moving in a circular path with a constant speed ‘v’ and radius ‘R’. We will draw velocity vectors for the wooden block at successive time intervals.

By transferring the tails of these velocity vectors to coincide at a single point, we will observe how the velocity vector changes direction and appears to rotate. The change in velocity (Δ V) will be represented by the base of an isosceles triangle formed by rotating a velocity vector through a small angle.

**Required Items:**

- Wooden block
- Circular path with marked radius ‘R’
- Drawing paper
- Ruler
- Protractor

**Step by Step Procedure:**

- Place the wooden block on the circular path of radius ‘R’.
- At regular time intervals (e.g., every second), observe the position of the wooden block and draw the velocity vector from its position tangent to the circular path, representing its direction and magnitude.
- Repeat this process for several time intervals, marking all the velocity vectors on the drawing paper.

**Experiment Observations: **

- The velocity vectors drawn on the paper will appear to be tangent to the circular path at each time interval.
- As more velocity vectors are drawn, they will form a series of closely spaced vectors pointing in different directions, indicating the continuous change in the direction of velocity.

**Precautions:**

- Ensure the wooden block’s motion is as close to uniform circular motion as possible, with constant speed ‘v’ and a circular path of radius ‘R’.
- Be accurate while drawing the velocity vectors to obtain meaningful observations.

**Lesson Learnt from Experiment:**

The experiment demonstrates that when an object moves in uniform circular motion, its velocity vector changes direction continuously. By drawing successive velocity vectors, we observe that they form a polygon that approximates the circular path.

The smaller the time intervals and the corresponding angles of rotation for the velocity vectors, the more accurate the approximation. Ultimately, the sum of the magnitudes of the changes in velocity during a complete revolution will be equal to the circumference of the circular path (2∏v).