Page 86 - Physics - XI

Procedure

1. Set up the experimental setup as shown in the Fig. 6.1. The experimental table should be horizontal.
2. Release the steel ball from A, on either of the two inclined planes.
3. Note the vertical height AB (or x) of the point A from the table using a meter scale and a plumb line.

4. After reaching the lowest point O, the ball starts heading towards point F of the other inclined plane.
Note the point F up to which the ball reaches the inclined plane on the other side and note the vertical
height FE (or y). Record the observations. At the time of observing the highest position of the steel ball
on other plane, observer has to be very alert as the ball stays at the highest position only for an instant.

5. Now, shift the wooden block w and w kept under either of the two planes towards the centre point O by
1
2
a small distance. Now, the angle of the slope of one of the planes would be larger than that of the other.
6. Release the ball again from point A on one of the two planes and mark the point F on the other plane
up to which the steel ball rolls up. Also, fi nd the vertical height FE.

7. Repeat steps (5) and (6) for one more angle of the slope of the inclined plane.
8. Repeat the observations for another point of release on the same inclined plane and note the observations
in the observation table.

Observations
Table for studying the conservation of energy of a ball using double inclined tracks

Reading on inclined plane from Reading on the inclined plane on which the ball
S. which the ball is rolled down rolls up Diff erence,
(x – y)
No. Position of Vertical height Position of mark up to Vertical height Mean (cm)
Mark A AB, x (cm) which the ball rolls up, F EF, y (cm) y (cm)

1. F =
2. G =
3. H =

1. F =
2. G =
3. H =

Result

From the observations, it is clear that the initial and fi nal vertical heights are same within the limit of
experimental error. Therefore, the rolling steel ball has same initial and fi nal potential energy, though
during the rolling motion the energy changes into kinetic energy. The above result shows that the sum of
kinetic and potential energy possessed by a ball rolling down an inclined plane remains constant.

Precautions
1. The double inclined plane should be properly cleaned by a tissue paper soaked in benzene to make it

almost frictionless.
2. The inclined planes should not be shaky.

84