3. Complete Activity 9.3 (Page 97). Draw a straight line on the ground with chalk powder or lime and ask one of your friends to stand 1 to 2 m away from it. Let your friend gently roll a ball along the ground in a direction perpendicular to the line. Note the time at the moment the ball crosses the line and also when it comes to rest (Fig. 9.6). How much time does the ball take to come to rest? Measure the distance between the point at which the ball crosses the line and the point where it comes to rest. You can use a scale or a measuring tape. Let different groups repeat the activity. Record the measurements in Table 9.3. In each case calculate the speed of the ball.
Answer:
The Activity 9.3 can be carried out in the following way:
Aim: To measure the speed of the rolling ball.
Materials Required: Ball, chalk powder or lime, stopwatch or wristwatch, scale or measuring tape.
Procedure:
(i) Mark a straight line on the ground with chalk powder or lime.
(ii) Ask another person to stand 1 to 2 m away from the line and gently roll a ball along the ground in a direction perpendicular to the line.
(iii) Using your stopwatch or wristwatch note the time when the ball crosses the line and also when it comes to rest. Note how much time it takes to cover distance d and recordit in Table 9.3.
(iv) Measure the distance d using a scale or measuring tape and record it in Table 9.3.
(v) Repeat the activity with different groups and record the measurements in Table 9.3.
Observations:
The completed Table 9.3 is shown below:
Table 9.3 Distance moved and time taken by a moving ball
| Name of the group | Distance moved by the ball (m) | Time taken (s) | Speed = Distance/Time (m/s) |
| Group 1 | 2 | 2 | 1 |
| Group 2 | 1 | 1 | 1 |
| Group 3 | 2 | 3 | 2/3 |
| Group 4 | 3 | 3 | 1 |
Conclusions:
The speed of the ball = Distance/Time varies depending on the distance moved and time taken.
“How much time does the ball take to come to rest? Let different groups repeat the activity. Measure the distance between the point at which the ball crosses the line and the point where it comes to rest. You can use a scale or a measuring tape. Let different groups repeat the activity. Record the measurements in Table 9.3. In each case calculate the speed of the ball.” – Solved.
Related Links:
Solution to Extended Learning Problem 1
Solution to Extended Learning Problem 2
Solution to Extended Learning Problem 3
Solution to Extended Learning Problem 4
Solution to Activity 9.1
Solution to Activity 9.2
Solution to Activity 9.3
