Introduction

In this science experiment, we will learn to determine the pulse velocity of a slinky or stretched string.

Pulse Velocity

1. A pulse is a disturbance produced inside the ends of an object when moving.
2. Pulse velocity is the distance traveled by pulse per unit time.

Pulse Velocity = Distance traveled/ time taken.

Aim

The aim of our experiment is to determine the pulse velocity of a slinky or stretched string.

Apparatus Required

1. A slinky or a spring,
2. A stopwatch,
3. A metre scale,
4. A strong support.

Theory

A pulse is a disturbance produced inside the ends of the spring when stretched.

Pulse velocity is the distance travelled by pulse per unit time.

Pulse Velocity = Distance travelled/ time taken.

Procedure

Step 1. Tie one end of the slinky with solid support.

Step 2. Measure its length with the help of a metre scale.

Step 3. For transverse waves, create a disturbance in the slinky by moving its other end up and down vertically.

Step 4. For longitudinal waves, create a disturbance in the slinky by moving its other end back and forth.

Step 5. In this way, we create a pulse travelling to the end fixed with solid support.

Step 6. Create a wave by producing a pulse continuously.

Step 7. Start the stopwatch when the first disturbance is created and stop when the last pulse hits the rigid support.

Step 8. Now note down this timing.

Step 9. Do this experiment 3 – 4 times with different pulses generated and record your observations.

Observation

1. Least count of the stopwatch = ………..
2. Length of slinky, S = …………..

Mean velocity = (V1  + V2 +  V3)/ 3

Result

The pulse velocity of a stretched string or a slinky = ……… m/sec.

Precautions

1. Slinky should be fixed firmly with rigid support.
2. Start the stopwatch immediately after the first pulse and stop it immediately after the last.
3. There should be a time interval between two successive pulses.
4. The slinky should be error-free and mass-less.
5. Measure the zero error of the stopwatch.
6. Stopwatch should be in the proper condition and working correctly.

Conclusion

In this way, we have seen how we can determine the pulse velocity of a slinky or stretched string.

Viva Questions with Answers

Q.1 What was the aim of this experiment?

ANS. To determine the pulse velocity of a slinky or stretched spring.

Q.2 What is the unit of pulse?

ANS. Metre/Second.

Q.3 What is slinky?

ANS. A slinky is an elastic helical spring.

Q.4 What kind of wave was travelling on slinky?

ANS. Mechanical waves.

Q.6 Describe the difference between a wave and a pulse.

ANS. A wave is produced by the continuous disturbance and repeats after a fixed interval of time, while a pulse is produced by a single disturbance in the medium and does not repeat itself.

Q.7 What was the nature of the pulse generated in slinky?

ANS. Transverse wave

Q.8 Why is it preferred to take a slinky of long length?

ANS. Because of the high pulse velocity generated, it is always advised to take a long slinky so that pulse can be measured perfectly.

Q.9  Which physical quantity travels along the length of the slinky when a pulse is sent?

ANS Energy

Q.10 Why in this experiment it is not given to measure the average velocity with different lengths?

ANS. Because pulse or wave is inversely proportional to the square root of mass per unit length. Pulse velocity depends on length; therefore, it will give a different value for different lengths.

Vikram Sarabhai

An Indian physicist and astronomer.