Answer to Question #3862 in Mechanics | Relativity for mia




 A wagon with a width of 2.4 m, moving at a speed of 15 m per second, was shot through by a bullet perpendicular to the movement of the wagon. The distance between the two bullet holes in the wagon&rsquo;s walls is 6 cm. What is the speed of the bullet ?
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the value of head loss due to friction using chezy formula with constant c= 60 for a fluid, flowing through a 30 cm diameter and 70 m long pipe. velocity of fluid inside the pipe is 5 m/s. the distance covered by a car in 5 h if it is moving with a speed of 75 km/h is\_\_\_\_\_\_\_\_? a bob of mass m is suspended by inextensible string of length l from a fixed point. the bob is given a speed of at the bottom point. find the tension in the string when string deflects through an angle 120 degree from vertical. u (initial velocity) = 18 km/hr 
t ( time )= 2.5 sec
v( final velocity) = 0 m/s
from, the first equation of motionv = u +  a×t0 = 5 +  a×2.5a = - 2 m/s2 let the speed of train = x km /hlet the speed of car = y km/hcase 1 : 120 km by train and 480 by cartime taken to travel 120 km by train = 120x hrstime taken to travel 120 km by car = 480x hrsaccording to first condition :120x + 480y = 8⇒1x + 4y = 115     
1case 2 : 200 km by train and 400 by cartime taken to travel 200 km by train = 200x hrstime taken to travel 400 km by car = 400x hrsaccording to second condition :    200x + 400y = 82060 = 813 = 253         as, 20 min = 2060 hr = 13 hr⇒1x + 2y = 124     
2subtracting 2 from 1, we get      2y = 115 - 124⇒2y = 8-5120⇒y = 80now, from 1, we get    1x + 480 = 115⇒1x = 11 - 120 = 160⇒x = 60so, speed of train = 60 km/hspeed of car = 80 km/h hint: here, we will proceed by finding out the relative speed between the two cars and then using the formula i.e., time taken$ = \dfrac{{{\text{distance travelled}}}}{{{\text{speed}}}}$ to determine after how many hours these cars will meet each other.complete step-by-step answer:given, distance between the two cars d=160 kmstarting time for both the cars when they left their respective initial positions a and b is 8:10 amspeed of the first car, x=50 km per hourspeed of the second car, y=30 km per hourin order to obtain the relative speed between these two cars which are moving towards each other (i.e., in opposite directions), the individual speeds of these cars will be added.so, the relative speed between the two given cars, r= x+y=50+30=80 km per houras we know that, time taken$ = \dfrac{{{\text{distance travelled}}}}{{{\text{speed}}}}$so, time when both the cars will meet=$\dfrac{{{\text{initial distance between both the cars}}}}{{{\text{relative speed between the cars}}}} = \dfrac{{\text{d}}}{{\text{r}}} = \dfrac{{160}}{{80}} = 2$ hours.after 8:10 am, both the cars which are initially at different places a and b will meet each other in the next 2 hours.therefore, time when they will meet each = 8:10 am + 2 hours = 10:10 amhence, option a is correct.note: in this particular problem, since the given two cars are moving in opposite directions (or moving towards each other) that’s why the individual speed of the cars are added in order to determine the relative speed between them but if they were moving in the same direction then the relative speed between these cars would have been obtained by subtracting the individual speed of these cars. miles/hour is just that.
 
(3/4)/(1/12) = (3/4)(12) = 9 mph v = (4/3)πr³ 

dv/dt = 4πr².dr/dt

so, when the diameter is 20 cm we have:

-4π = 4πr².dr/dt

hence, dr/dt = -1/r²

i.e. dr/dt = -1/10² => -1/100

now, d = 2r

so, d(d)/dt = 2.dr/dt

=> d(d)/dt = -1/50 cm/hour

or, -0.2 mm/hour

:)> we first define our axisupward is along + y direction of axiseastward is along + x direction of axisvelocity of a aeroplane = velocity of a bullet = a person on the earth will see the bullet having a resultant velocity and angle θ with the vertical (y axis)θ = angle with the vertical (y axis) answer: refractive index is defined as the ratio of the speed of light in a vacuum to its speed in a specific medium. refractive index is dimensionless. it is a number that indicates the number of times slower than a light wave would be in the material than it is in a vacuum. refractive index, represented by symbol n, is the velocity of light in vacuum divided by the velocity of light in a medium. the formula of the refractive index is, n = c/ν where n = refractive index. c = velocity of light in a vacuum ( 3 × 108 m/s). v = velocity of light in a substance. snell’s law clarifies the relation between the angle of incidence and angle of refraction. so, there are two formulas for calculating the refractive index of a medium. let us imagine that a ray of light is travelling from a medium a to another medium b. then conferring from snell’s law, .