When the ruler is broughı near the inetal knob, it repels electrons in the metal. Electrons move away froni the ruler and down the metal rod. The knob now has a positive charge. The thin pieces of metal foil at the bottom of the metal rod now have a negative charge.
D. How high do the sound waves go
Answer:
45.6m
Explanation:
The equation for the position y of an object in free fall is:

With the given values in the question the equation has one unknown v₀:

Solving for t=1:
1) 
To find the hight of the tower you can use the concept of energy conservation:
The energy of the body 1 sec before it hits the ground:
2) 
If h is the height of the tower, the energy on top of the tower:
3) 
Combining equation 2 and 3 and solving for h:
4) 
Combining equation 1 and 4:

Answer:
The expression for the period of the pendulum is
T=2π√l/g
Explanation
Kindly find attached document for the analysis of the pendulum and the derivation for the period
What is a simple harmonic motion?
Simple harmonic motion is defined as the to and fro motion of an object or a particle whose acceleration is directly proportional to its displacement from a fixed point and is always directed towards that point.
1. Take a breaker
2. Put a sieve on it
3. Pour the mixture and shake the sieve gently
4. Wait for the flour to fall. After the flour falls pour the rice from the sieve into other beaker then do experiment again for fair testing(optional)