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

Explain how the resistance of a filament lamp changes as the potential difference across it increase

As the potential difference across the filament lamp increases the current across the lamp also increases due to Ohm's law.The increase in current flow also causes the lamp to heat …

Explain, with reference to the Schwarzschild radius, why the sun isn’t a black hole.

The Schwarzschild radius of the sun can be calculated using Rs= (2GM)/c². Substitute in the mass of the sun (M=210³⁰), the speed of light (c=3 …

In an isolated container contains 1kg of ice at 0 oC. 1kg of warm water (323K) is poured into the container. How much ice (in kgs) remains after the system returns to thermal equilibrium? (by the end of the process?)

As this is an isolated container, we know that the heat transfer with the environment is zero. Since the specific latent heat of ice is a magnitude bigger than the …

Assuming no friction, describe the motion of a simple pendulum released from rest at t=0 at amplitude A? Provide information about its speed and position at characteristic times during one period. [The 1D equation of motion is described by a cosine]

The displacement of the bob of mass m is given by the equation x(t)=A cos(w*t), with no phase offset as given by the boundary conditions (zero speed at t=0). By …

Describe one method by which the distance to stars from Earth is measured, and one modern improvement to this method which increases its accuracy.

One such method is Stellar parallax. When observing stars in the night sky, stars which are further away from Earth appear to 'move' less across the sky as the earth …

Why do Physicists take multiple readings in experiments?

Taking multiple readings allows for errors (known as anomalous data points) to be spotted.For example if you were to take just one reading in an experiment and this was wrong, …

The speed of light is 3.0 × 10^8 m/s. The wavelength of yellow light is 5.8 × 10^−7 m. Calculate the frequency of yellow light. State the unit.

We know that frequency is 1/time, thus the unit is Hz (equal to s^-1). To calculate the frequency value, we use the equation Frequency = Wavespeed (m/s) / Wavelength (m). …

What's the difference between a vector and a scalar?

A scalar is a single quantity giving an "amount" of something - it only has a magnitude. For example, temperature or energy are represented by a single value. On the …

How much thermal energy does a 1 kg steel block with a specific heat capacity of 450 J/kg°C lose when it cools from 400°C to 60°C?

E=mc0E = 1 x 450 x (400-60)E = 1 x450 x 340E = 153,000J

A mass of 2.5kg is raised by a height of 8m in 36 seconds using an electronic motor. Calculate the power of the motor.

Power = Work / Time. Work = mgh = 2.59.818 = 196.2 J. Power = 196.2 (J) / 36 (Seconds) = 5.45 W.

What is a chain reaction?

When neutrons from one reaction fire off to cause further reactions.

A student is investigating how the pressure exerted by a gas varied with the volume of the gas. The initial pressure was 1.6x10^5 Pa, with the volume being 9.0cm^3. Calculate the volume of the gas when the pressure was 1.8x10^5 Pa

pxV=constant
(1.6x10^5) x (9.0) = (1.44 x 10^6)
p= (1.44 x 10^6)/(1.8 x 10^5) = 8 cm^3

A balloon's volume is 0.002m^3 at room temperature (20°C). What volume will the balloon occupy when it is cooled to -5°C? Give your answer to 3 significant figures.

(Charles' Law) V₁/T₁ = V₂/T₂
(Rearrange) V₂ = (V ₁T₂)/T₁
(What are all the values in the equation?) V₁ = 0.002m^3 T₁ = 20°C T₂= -5°C V₂= ??
(Convert all …

Houses lose majority of their energy through the roof and windows. State the three methods of energy transfer. For the roof and windows respectively, describe one adaptation that could be made to improve their efficiency and explain their method.

Conduction, Convection, Radiation
Roof: Insulation. Material reduces conduction as it is a greater inductor of heat than air. Material reduces convection currents as the air gaps are now too small …

Write the equations of motion for constant acceleration and describe each term involved. Explain how to apply these equations of motion to calculate the horizontal and vertical components of a projectile moving under the force of gravity only.

The equations of motion for constant acceleration are obtained from Newton's laws of motion. They are sometimes known as the SUVAT equations and can be used to calculate components of …

As a student rubs his feet along the carpet in his living room, he becomes charged. After this he places his hand on a metal radiator and receives an electric shock. Explain what charge the student obtains, why, and why he receives a shock.

As the student rubs his feet on the carpet, negatively charged electrons are transferred from the carpet to his feet. This gives the student AS A WHOLE a net negative …

What is the doppler effect?

The Doppler effect is caused when waves (such as light or sound waves) are emitted from a moving source which causes an increase or decrease in the wavelength of the …

What is the difference between longditudinal and transverse waves?

For transverse waves, the oscillations are perpendicular to the direction of travel. For longditudinal waves the oscillations are parallel to the direction of travel.

What is the structure of atoms

There are three elementary particles that make up the atom. Those being: the proton, the neutron, and the electron. Both the proton and the neutrons are nucleons, and they reside …

Describe the transfers of energy occurring when a ball is thrown vertically up in the air and falls back down to Earth, assuming there is no friction from the air.

When the ball is thrown, chemical energy in the muscles of the person is transferred to the ball as kinetic energy. As the ball rises, kinetic energy is transferred to …