Answer:
Mechanical waves
Explanation:
Waves are periodic oscillations, that carry energy, but not matter.
Waves are classified into two types:
- Mechanical waves: these waves are produced by the oscillations of the particles in a medium, which can oscillate along the direction of propagation of the wave (longitudinal wave) or perpendicular to the direction of motion of the wave (transverse wave). These waves can only propagate in a medium, so they cannot travel in a vacuum. Examples of mechanical waves are sound waves.
- Electromagnetic waves: these waves are produced by the oscillations of electric and magnetic field. They are transverse waves. They are the only type of wave able to propagate through a vacuum (so, through space).
Therefore, the waves that need molecules in order to transfer energy are mechanical waves.
Answer:
v = 26.52 m/s
Explanation:
Here we know that as she passes the flag she will gain some speed
so here we can say that
Work done by all forces = change in kinetic energy of the system
so we will have

here we know that



h = 39.78 m
d = 27.81 m
so we have



Answer:
A force unit is defined as the product of a mass unit and a unit of acceleration.
Answer:
In parallel circuits all components have the same voltage. In series circuits all components have the same current.
Explanation:
Voltage in a circuit is akin to pressure in water, while current is akin to flow in water.
Voltage and current are related to resistance by Ohm's law:

Where:
V: voltage
I: current
R: resistance
In a parallel circuit all the terminals of one side of the devices are connected together. This is known as a node. Nodes have a certain voltage. Devices connected in parallel will have one node on each side, and each node will have it's own voltage. Current will flow through each component independently depending on their resistance, so it is not the same for all of them.
In a series circuit components are connected one after the other, the current that flows through one must continue and flow through the next, so they all have the same current. But since they might have different resistances they might have different voltage differences between their terminals.
Parallel connection is useful when you have devices that require a specific voltage, such as household appliances. All wall power outlets are connected in parallel.
Series connection is useful when you want to control current. When you use a LED you must be careful not to apply an overcurrent, so a series resistor is commonly used to limit the current.