### Physics Questions and Answers

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

### 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

### 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

### 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

### Why is a parallel circuit arrangement best for house wiring?

In a house, there are many electrical appliances that have to run independent of each other. If one appliance is turned on or off it should not affect the other appliances. This is not possible if...

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

### 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

### 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

### 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

### 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

### 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

### 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

### 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

### What is the maximum height the ball reaches? A ball is thrown vertically upward from the roof of a 64 foot tall...

The ball is thrown upwards at 96 ft/s from the roof of a building which is 64 foot tall. The height of the ball after t seconds is given by the function: s(t) = 64 + 96t - 16t^2 To find the maximum...

Physics

### Calculate the angle of projection, with the horizontal, for a projectile for which the maximum height is equal to the...

The angle of projection for which the maximum height of the projectile is equal to the horizontal range has to be determined. Let the required angle of projection be A and object is projected at V...

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

### 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

### Why do heavier things fall faster than lighter things if dropped from a certain height ? related to gravitational force.

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 wire has a resistance R. If the length of a wire is doubled and the radius is doubled, what is the new resistance...

The resistance of a resistor is given by the formula `R = rho*l/A ` where `rho` is the resistivity of the material the resistor is made of, l is the length of the resistor and A is the...

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

### 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

### 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

### 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

### 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

### 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 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

### 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

### What is the distance traveled by the car during the period of acceleration in the following case: A car that is...

The car was initially travelling at 80 km/h. It then accelerates at 12km/h^2 for 22 seconds. 22 seconds is equal to 22/3600 hours. Therefore the speed of the car after the period of acceleration...

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

### 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

### The density of ice is 917 kg/m^3. what fraction of the volume of a piece of ice will be above water, when floating in...

When a body is placed in a fluid, there is an upward force exerted on the body that is equal to the weight of the fluid displaced by it as it sinks into the fluid. When this force is equal to the...

Physics

### What is the magnitude of the acceleration of the chair, and the magnitude of the normal force acting on the chair in...

Yusef pushes the chair of mass 45 kg across a carpeted floor with a force of magnitude 144 N directed 35.0 degrees below the horizontal. The magnitude of the frictional force between the carpet...

Physics

### A ball rolls off the top of a stairway horizontally with a velocity of 4.5m/s. Each step is 0.2m high and 0.3m wide....

The ball rolls off the top of a stairway horizontally with a velocity of 4.5m/s. Each step is 0.2m high and 0.3m wide. Let the ball land on the nth step. The horizontal distance covered by the ball...

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 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

### 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

### Two tugboats pull a disabled supertanker. Each tug exerts a constant force of 1.50*10^6 N, one at an angle 15.0...

Two tugboats pull a disabled supertanker. Each tugboat exerts a constant force of 1.50 X 10^6 N, one at an angle 15.0 degrees west of north, and the other at an angle 15.0 degrees east of north, as...

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

### An airplane has a mass of 2.00 x 10^6 kg, and each wing has an area of 1200 m^2. The air flows past the lower surface...

As an airplane flies, the speed of air passing over the top of the wing is higher than the speed at which air flows below the wing. This creates a differential in the pressure above and below 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

### A convex mirror has a focal length of −27 cm. What is the object distance if the image distance is −16 cm?

The following formula relates object distance, image distance, and focal length for convex mirrors: 1/(focal length) = 1/(object distance) + 1/(image distance) or 1/fo = 1/do + 1/di The image...

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

### What will happen if an ice-cube with a metal piece inside, floating in water melts. Will level of water remain same...

Wow, that's a cool question. I want to have a crack at it! The addition of the ice cube would raise the water in the glass because it will displace the water currently in the glass. As the ice...

Physics

### What is the number of excess electrons on each sphere in the following case? Two small spheres spaced 35 cm apart...

The force between two bodies with a charge q1 and q2 and a distance of separation r is given by Coulomb's law as q1*q2/(4*pi*e0*r^2). 1/(4*pi*e0) = 8.987*10^9 Nm^2/C^2 Now the distance between the...

Physics

### A battery of e.m.f 15V and internal resistance 2 ohm is connected to two resistors of 4 ohm and 6 ohm joined in: (a)...

The emf of the battery is 15 V and the internal resistance is 2 ohm. The battery is connected to a circuit made of 2 resistors of 4 ohm and 6 ohm. a. When the resistors are joined in series, the...

Physics

### A 0.160 kg hockey puck starts from rest and reaches a speed of 22 m/s when a hockey stick pushes on it for 1.2 m...

The hockey puck has a mass 0.16 kg. It starts from rest and reaches a speed of 22 m/s, during which the distance traveled is 1.2 m. Initially the puck has no kinetic energy. After 1.2 m the kinetic...

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

### 1. A ray of light passes from air into water at an angle of 30.0 degrees. Find the angle of refraction. (22.1 degrees)

Refraction is the phenomenon of the "bending" of rays of light as they pass the boundary between two media, for example, air and water. It happens because the light propagates with different speeds...

Physics

### Why does a helium balloon stop rising after it reaches a particular height?

A helium balloon rises upwards due to the force of buoyancy exerted by the air it displaces. As helium is lighter than air, the total weight of air that the balloon displaces is more than the...

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