## Physics Questions and Answers

Physics

### What is the formula for pressure?

The formula for pressure is P = F/A In this equation, P stands for pressure while F stands for force and A stands for area. Pressure is typically measured in a unit called the Pascal. So what this...

Physics

### How are impulse and momentum applied in an egg drop challenge? The challenge was to construct something protective...

Impulse is the change in momentum of an object. There are two impulses that your egg design will have to deal with. The first impulse is from the drop itself. Its momentum will increase due to the...

Physics

### The position vector of a particle is given by r(t)=t^3*i+t^2*j. What are it's velocity speed and acceleration when t=2

We have the position vector given in terms of time t. r(t) = t^3*i + t^2*j To find the velocity vector we have to differentiate r(t) with respect to time. r'(t) = 3t^2*i + 2t*j The vector...

Physics

### A bullet is fired horizontally out of a gun at the same time another is dropped from the end of the barrel. The one...

They both hit the ground at the same time. So your answer is C. Gravity works on the bullets just the same regardless of velocity. The bullets have to be the same calibre and weight for this to...

Physics

### What is the mass of air in a room measuring 5m X 10m X 10m?

In order to find the answer to this question, you need to know the following equation: m = dv Where m is mass, d is density, and v is volume. In this case, you are looking for mass, you have...

Physics

### Explain how to measure the volume of an irregular shaped object if it floats in water.

The displacement of water is an excellent way to measure the volume of a solid provided that the solid does not dissolve in water and that it does not float. If the object floats then it will not...

Physics

### Why is the current flow greater in a parallel circuit than it is in a series circuit?

For a potential difference V across a resistor R, the current I that flows through the resistor is given by Ohm's law as I = V/R As current is inversely proportional to resistance, for the same...

Physics

### A layer of oil with density 800 kg/m^3 floats on of water with density 1000 kg/m^3. A block floats at the oil-water...

Let the volume of the block be V and the density D. The mass of the block is D*V. In an oil-water interface with oil having a density of 800 kg/m^3 floating on water with a density of 1000 kg/m^3,...

Physics

### What is the illuminance (in lm/m^2) on a desktop if the lamp is 0.9 m above it? The equation of the illuminance, E,...

Rearranging terms, E ( 4(3.1416)d^2 ) = P, so E ( 4(3.1416)[.9m^2] ) = 1200 lm E ( 12.57 [.81m^2] ) = 1200 lm E (10.17m^2) = 1200 lm E = 1200 lm / 10.17 m^2 E = 118 lm/m^2

Physics

### Is a hockey stick used as lever? What kind of lever is it?

A hockey stick is used as a lever. When you hold a hockey stick, the hand with which you hold the stick at the top end serves as the fulcrum. The other hand with which you catch the stick in the...

Physics

### What is a unit of mass?

Mass is "the amount of stuff" in an object. That is, the amount of atoms and molecules present. Mass in science, is measured in the metric system using units such as kilogram (about 2.2...

Physics

### You throw a basketball straight up into the air. Describe what happens to the kinetic energy and the gravitational...

When the basketball is thrown up an initial velocity is imparted to it. This gives the ball a kinetic energy equal to (1/2)*m*v^2 where m is the mass of the ball and v is the velocity with which it...

Physics

### Water has a density of 1000kg/m^3; what does this mean? What is its density in g/cm^3?

The meaning of the original statement is that if you have a cubic meter of water (an amount of water that is one meter in height, one meter in width, and one meter in depth), that amount of water...

Physics

### Can an object have kinetic energy and potential energy at the same time?

Yes, an object can have both of these at the same time. Potential energy is energy that is stored in an object. Kinetic energy is the energy that is associated with motion. So what you have to...

Physics

### A table tennis ball has an average density of 0.084 g/cm^3 and a diameter of 3.8 cm. What force can submerge the ball...

The density of the table tennis ball is 0.084 g/cm^3. This has to be converted in terms of SI units. It is equal to 0.084*10^-3/(0.01)^3 kg/m^3 = 84 kg/m^3. The density of water is 1 g/cm^3 which...

Physics

### A person is standing on a scale in a elevator accelerating downward. compare the reading on the scale to the person's...

The safe answer is C. See below why it could also be D: The best way to think of weight is this: weight is the measurement of resistance of a given mass to falling. On the earth, everything that...

Physics

### PHYSICS help If a metal wire has its length doubled and its diameter tripled, by what factor does its Young's modulus...

The Young's modulus is a constant for metals in the range of values of stress for which Hooke's law is valid. It can be determined by the relation: Young's modulus= Tensile Stress/ Tensile Strain....

Physics

### In the context of conservation of energy what effect does friction have on kinetic energy and gravitational potential...

The law of conservation of energy states that the total energy in an isolated system does not change. It may change form, for example mechanical energy may get converted to thermal energy,...

Physics

### Density Of Mercury

The term "relative density" means the same as "specific gravity." It is a measure of how dense one thing is when compared to a given reference. The reference is usually water. With respect to...

Physics

### Walking on pebbles in bare feet is more painful than walking on sand. Why?

This is because of the amount of force that is put on your foot and the area over which the force is applied. Since pressure = force/area, the same force on a smaller area means more pressure....

Physics

### How fast must a ball be thrown upward to reach a height of 12 m?

When a ball is thrown vertically upwards, there is an acceleration acting on it due to the gravitational force of attraction of the Earth equal to 9.8 m/s^2. This acts in a direction vertically...

Physics

### A ray of light strikes a mirror at an angle of 30 degree to the mirror surface. What is the angle of reflection?

If I understand this question correctly, the angle of reflection should be 30 degrees with respect to the mirror as well. The angle of the incoming ray and the angle of the ray that is reflected...

Physics

### 3 resistors of 5 ohm each are connected, 2 in parallel and the third in series to the others. What is the total...

When two resistors with resistance R1 and R2 are connected in parallel, the equivalent resistance of the configiration is given by 1/R = (1/R1 + 1/R2). And for two resistors R1 and R2 connected in...

Physics

### At sea level, what is the approximate value of atmospheric pressure in Pa, in mmHg and in atm? (where g = 10 N/kg)

At sea level, the approximate value of atmospheric pressure in those units of measure is as follows: 101.3 kPa which is how it is usually expressed. In pascals, it is 101325 pascals. The first of...

Physics

### What is the energy of a quantum of light having a frequency of 6.0 x 10^14 hertz in electron-volts (eV)?

The energy of a quantum of light or a photon is given by the formula E = h*nu = h*c/lambda, where nu is the frequency of the light, lambda is the wavelength, c is the speed of light and h is the...

Physics

### When a student drops a tennis ball what happens to its velocity and acceleration after it has been released?

The ball is stationary in the students hand when it is dropped. Once the student drops the ball, it is acted upon by the gravitational force of the Earth. This force creates an acceleration of 9.8...

Physics

### Unbalanced forces can cause an object to do three things. What are they?

Forces are considered balanced when all of the combined forces lead to no change in the motion of the object. For example, when a book is sitting on a table, the force of gravity is pushing...

Physics

### Which are the most conductive and least conductive metals?

The electrical conductivity of a metal has the SI units Siemens/meter. This is a reciprocal of the resistivity that is expressed in terms of ohm*m. Electrical conductivity of a metal is not the...

Physics

### A man inside an insulated metallic cage doesn't receive a shock when the cage is highly charged. Why?

A man in a metallic cage is not affected even when the cage is highly charged due to what is known as the Faraday cage effect. In a state of equilibrium, charges are as far from each other as...

Physics

### Are kinetic energy and height inversely proportional to each other or directly proportional to each other? Why?

At a height h, the gravitational potential energy P of an object with mass m is given by the relation P = m*g*h. If the object is considered to be a closed system, it is assumed that there is no...

Physics

### Two long straight wires carrying the same current I and separated by a distance r exert a force F on each other. If...

According to Ampere's law, the force between two wires carrying a current I1 and I2 and which are separated by a distance r is given as F= 2*K*I1*I2 / r, where K is a constant. In the problem, when...

Physics

### Why do heavier things fall faster than lighter things if dropped from a certain height ?

Most of the time, people ask this question with the idea of a Newtonian "feather vs. bowling ball" concept in mind. Based on those terms, the typical answer is correct: two objects will fall at the...

Physics

### A 145g baseball is thrown with a speed of 25m/s . How much work was done on the baseball to reach this speed if it...

A 145 g baseball is thrown with a speed of 25 m/s. When the thrower picks up the ball it is at rest. When it leaves the hand of the person that is throwing the ball it has a speed of 25 m/s. An...

Physics

### A force of 200 N acts on an area of 4 m^2. What is the pressure and what would be the pressure if the same force...

The pressure would be doubled if the same force acted on half the area. The pressure in the first scenario is 50 N/m^2 while the pressure in the second scenario is 100 N/m^2 The way you get this is...

Physics

### A 66-kg skier, initially at rest, slides down a hill 25 m high, then has a completely inelastic collision with a...

The 66 kg skier slides down a hill 25 m high. The potential energy of the skier at the top of the hill that has a height of 25 m is given by PE = m*g*h = 66*9.8*25. At the bottom of the hill all...

Physics

### In the following physical systems that undergo simple harmonic motion, state which physical quantity or quantities...

The simple harmonic motion is by definition the motion of a point which is subjected to a force that is proportional to the deviation of the point from the equilibrium position``. For mass spring...

Physics

### A 5 N force which acts along the direction vector (2,3) moves an object from A (1,3) to B (3,7). Find the work done...

The applied force moves an object from A( 1 , 3) to B( 3 , 7). The slope of the line joining these points is (7 - 3)/( 3 - 1) = 4 / 2 = 2. The slope of the direction vector is 3/2. The angle...

Physics

### What is the equivalent spring constant when springs are connected in parallel and in series?

When a spring is extended or compressed from its equilibrium length, the change in length is related to the force applied by the relation F = -kx, where F is the force applied, k is the spring...

Physics

### A 10.2 cm diameter wire coil is initially oriented so that its plane is perpendicular to a magnetic field of 0.98 T...

Remember we have the expressions: `E = A * (dB)/(dt)` `A = pi r^2` `E = pi r^2 (dB)/(dt)` where: A = area of the coil r = radius = diameter/2= 10.2/2 = 5.1 cm = 0.051 m db = change in magnetic...

Physics

### What is the effect on the vertical height of the mercury column in a barometer of a) using a wider glass tube, b)...

The height of mercury above the bowl in a barometer is a measure of the pressure of air pushing on the mercury in the bowl. The mass of the mercury above the bowl times the force of gravity is...

Physics

### A car is moving 60km/h when the driver sees a signal light 40m ahead turn red. The car can slow with acceleration...

eNotes policy only allows for one question per submission so I have editted your question accordingly. I have decided to demonstrate the more difficult question so if you understand these concepts,...

Physics

### What is the secret to catching a water balloon without breaking it? Explain using physics.

When a water balloon is thrown towards a person it bursts when an attempt is made to catch it because the material that the balloon is made of cannot withstand a large force. The water filled in...

Physics

### By what factor does the kinetic energy of a car change when its speed is tripled? Multiple Choice: a) factor of 3...

The correct answer here is C -- it increases by a factor of 9. Here's why: The formula for kinetic energy is k = .5 mv^2 or k = .5*m*v*v Where k is kinetic energy, m is the mass and v is the...

Physics

### What happens to a object's kinetic energy if its speed changes, for example it becomes double or triple.

The kinetic energy of an object with mass m and which has a speed of v is given by (1/2)*m*v^2. The change in the kinetic energy of the object as the speed changes is proportional to the square of...

Physics

### How long would it take a radio wave to travel from Venus to Earth?

One major problem with intrasolar and interstellar communication is the vast distances involved. On Earth, radio communication is all-but instantaneous, because radio waves travel at the speed of...

Physics

### As a rocket moves away from the Earth's surface, the rocket's weight... Multiple choice: A) increases B) decreases...

The correct answer here is B -- the weight of the rocket decreases. The point of this question appears to be the difference between weight and mass. Mass is a measure of the amount that is in an...

Physics

### A 1.98 kg ball is attached to a ceiling by a 2.1 m long string. The height of the room is 5.95 m. The acceleration of...

Thte way you have worded this, the ball is below the ceiling, so the potential energy with respect to the ceiling is negative. PE = mgh, and since the zero position is the ceiling, the potential...

Physics

### Let the only forces acting on two bodies be their mutual interactions. If both bodies start from rest, show from...

The wording of this question is a bit confusing. It appears that the question is asking for an explanation of how force and mass are related to each other. That's a part of Newton's second law. The...

Physics

### A steel bridge is 1000m long at -20 degreesC in winter. What is the change in length when the temperature rises to 40...

The answer is D. This can be easily determined by using the formula for linear expansion due to temperature (or linear thermal expansion). This formula is stated as change in length = alpha times...

Physics

### How can a large force result in small power?

Power is defined as the ratio of work per time, or 1. Power = Work/Time Work is defined as Force times Displacement, or 2. Work = Force * Displacementso therefore3. Power = (Force * Displacement) /...

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