PHYSICS
HIGH SCHOOL

Answer:

Answer: The leaves will spread.

Explanation: Since the top of the electroscope has been touched initially by a positive glass rod, the charge on it is positive ( this is charging by conduction).

By bringing a negative charged rod towards ( but not touching the top) the top of electroscope means we will be charging the electroscope by induction. Charging by induction implies that an opposite charge of the conductor (negative charged rod) we are using to charge will be formed on the conductor that we want to charge (already positive charged electroscope)

In this case, our plastic rod is negative and it is brought towards the top of the electroscope ( which is already positively charged), there will be an induced positive charge on the electroscope.

So we have positive charge on the electroscope by a positive rod ( charging by conduction) and a positive charge from a negative rod ( charging by induction) thus the leaves will spread meaning the charges are repelling based on the fact that opposite charges attract and like charges repel

HIGH SCHOOL

Where is the magnetic field the strongest

Hello There!

A magnet has two poles called the north pole and the south pole. The magnetic field is always strongest at the poles of the magnet.

Answer:

at either point of the magnet

Explanation:

its equally strong at the north pole when compared with the south pole.

COLLEGE

A lead bullet of mass m traveling at vi penetrates a wooden block and stops. Assuming that 50% of the initial kinetic energy of the bullet is converted into thermal energy in the bullet and the specific heat of lead is c, write an expression that would allow you to determine the bullet's temperature increase.

Express your answer in terms of the variables m, vi and c.

Answer:

Explanation:

Given that

mass of the bullet = m

Speed of the bullet = vi

Therefore the kinetic energy of the bullet KE will be

Given that 50 % of the kinetic energy is converted into thermal energy.

KE'= 0.5 KE

The thermal energy Q is given as

Q= m c ΔT

Q=Heat

m=mass

c=specific heat capacity

ΔT=Temperature difference

Therefore we can say that

Q= KE'

Therefore the increase in temperature is given as

COLLEGE

A cat is on a merry-go-round that completes 1 full rotation in 6 seconds. The cat sits at a radius of 8.4 metres from the centre. Find the minimum coefficient of friction to prevent the cat from sliding off.

To solve this problem we will use the concepts related to the uniform circular movement from where we will obtain the speed of the object. From there we will go to the equilibrium equations so that the friction force must be equal to the centripetal force. We will clear the value of the coefficient of friction sought.

The velocity from the uniform circular motion can be described as

Here,

r = Radius

T = Period

Replacing,

From equilibrium to stay in the circle the friction force must be equivalent to the centripetal force, therefore

Here,

Coefficient of friction

N = Normal Force

m = mass

v = Velocity

r = Radius

The value of the Normal force is equal to the Weight, then

Rearranging to find the coefficient of friction

Replacing,

Therefore the minimum coefficient of friction to prevent the cat from sliding off is 0.9399

HIGH SCHOOL

What color of light has the shortest wavelength

Answer:

Violet

Explanation:

Electromagnetic waves consists of oscillating electric and magnetic fields that vibrate in a direction perpendicular to the direction of propagation of the wave (for this reason, these waves are also called transverse waves).

Electromagnetic waves are generally invisible to human eye, apart from a very small portion of it, called visible light.

Waves in the visible part of the spectrum appear to us as a different color, depending on their wavelength. From shortest to longest wavelength, we have:

Violet (380-450 nm)

Blue (450-495 nm)

Green (495-570 nm)

Yellow (570-590 nm)

Orange (590-620 nm)

Red (620-750 nm)

So we see that violet is the color with shortest wavelength.

Answer:

Violet

Explanation: