Physics Questions & Answers - Physics Doubts, Problems, Homework Solutions

In the early 20th Century the plum pudding model of the atom was replaced by the nuclear model of the atom, explain why this happened.

The plum pudding model defined the atom as a particle in which the charge and the mass of the atom was spread evenly. An experiment was set up in which …

Name and describe both of Kirchhoff's laws.

The Loop rule, this states that the sum of the potentials in a loop must be equal to 0.The Junction rule, this states that the sum of the current entering …

A footballer kicks a ball vertically upwards. Initially, the ball is stationary. His boot is in contact with the ball for 0.050s. The average resultant force on the ball during this time is 180N. The ball leaves his foot at 20m/s. Calculate the impulse

Impulse is Force x TimeThe force has been given as 180N. The time that the foot was in contact with the ball was 0.05sImpulse=FxtImpulse=180x0.05Impulse= 9Ns

How does heat transfer through convection work?

Convection is transfer of energy through movement of liquid particles. Let us take some steps back and revise a number of principles. First of all, you should remember the concept …

In the photoelectric effect, why is the kinetic energy of the electrons independent of the intensity of light?

In our situation, the stopping potential doesn’t let any electron to pass. When we increase the frequency of incident light, the electrons get more energy. We know it from equation …

What is meant by 'resolving a vector into its components'?

So, let's think of a vector as an 'instruction' - a guide telling us to move in a specific direction for a certain distance. (Draw arbitrary vector A here). This …

What are the three major radiations experienced by heavy unstable nuclei, and how does the penetrating power compare for each?

α - Emission of a Helium nucleus, it has the highest mass and lowest energy of the three types of radiation, it has a +2 overall charge due to its …

Why is the sky blue?

The Earth's atmosphere scatters incoming light from the sun. This incoming light is made up of lots of different colours. Each colour of light has a different wavelength and because …

A mass of 2kg is dropped from rest at a height of 10m. i) What is the initial GPE of the mass? ii) What is the final velocity of the mass when it hits the ground?

Part iGravitational Potential Energy (GPE) = mass x gravitational acceleration constant x heightGPE = 2 x 9.81 x 10 = 196.2JPart iiConservation of energy states that the …

If a car drives at 5 ms^-1 for 10 seconds and then 6 ms^-1 for 5 seconds, how far has it travelled in total?

The equation used here is speed = distance / time (s=d/t). Firstly the 30 ms^-1. Rearrange the equation to find distance (st=d). 5ms^-1 x 10s = 50m. The second stint …

Explain the difference between current and voltage

Current is defined as the amount of electrons that flow through a wire per secondVoltage is defined as the amount of energy that each electron carries as it passes …

What is meant by the conservation of energy?

Energy cannot be destroyed or created - it is always transferred between different objects in different forms. Hence, energy is 'conserved'. The most basic example is dropping a stationary rubber …

Can you explain the different ways heat can travel?

Heat can travel through 3 different processes: conduction, convection and radiation. Conduction is caused by atoms bumping into each other, transferring energy and therefore heat. An example of this would …

Waves on the surface of water are transverse waves. State one other example of a transverse wave.

Light wave.

Give an example of ionising radiation

gamma, beta, ultraviolet

What is the reaction force? (eg from the ground or table)

The reaction force is the force that the table exerts on an object which is pressing on it.
The reason there is a reaction force is because the table is …

What is the difference between a transverse and a longitudinal wave?

A wave is a transfer of energy of particles. In the case of a transverse wave, the particles oscillate perpendicular to their direction of movement (i.e it looks like they …

Explain the motion and forces on a falling object as it approaches terminal velocity.

Key points for understanding:

-The resultant force on the object is the vector sum of all forces on an object.

-Acceleration is a rate of change of velocity.

-Resultant …

Coal is a non-renewable energy resource. Name two other non-renewable energy resources.

oil and gas

What is the power dissipated by a 12 Ohm resistor when 2A of current run through it?

We know P=IV and that V=IR. Therefore as we are only given I and R in the question we can make the substitution for V so that P=I2R. …