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Orlov [11]
3 years ago
14

A swimmer swims 3/5 the width of a river at one velocity, then swims the remainder of the river at half her initial velocity. Wh

at was the average speed across the river?
Physics
1 answer:
SashulF [63]3 years ago
3 0
Let her initial velocity be U.

Let the width of the river be W.

She swims 3/5 the width of the river  at  U.

Remainder width =  (1 - 3/5) = 2/5.

She then swims 2/5 the width with velocity  U/2.


Average Speed  =  (Total Distance Traveled)  /  ( Total Time Taken).


Distance =  Speed * time

time  =  Distance /  Speed.

Time in first trip:    =    (3/5)W / U =   0.6W/U.

Time in second trip  =  (2/5)W / (U/2)  =  0.4W / 0.5 U =  0.8W/U

Total Distance Traveled =  W,  width of the river.

Average Speed  =      W  /  (0.6W/U  +  0.8W/U) =    W /  (1.4W/U)

                             =  W  *  U / 1.4W 
                              =    U/1.4
                              =  U * 10 / 14
                              =  (5/7) U.

Therefore Average speed is  (5/7) of the initial speed.


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A man stands on a platform that is rotating (without friction) with an angular speed of 1.0 rev/s; his arms are outstretched and
Airida [17]

Answer:

Explanation:

Given

N_1=1 rev/s

angular velocity \omega =2\pi N_1=6.284 rad/s

Combined moment of inertia of stool,student and bricks =6\ kg.m^2

Now student pull off his hands so as to increase its speed to suppose N_2 rev/s

\omega _2=2\pi N_2  

After Pulling off hands so final moment of inertia is

I_2=2\ kg-m^2

Conserving angular momentum  as no external torque is applied

I_1\omega _1=I_2\omega _2

6\times 6.284=2\times \omega _2

\omega _2=18.85\ rad/s

N_2=3 rev/s

7 0
3 years ago
A wooden block has a mass of 562 g and a volume of 72 cm3. What is the density?
dangina [55]
Mass/volume is density so it’s 562g/72cm^3 so it’s roughly 7.805g per cubic centimeter
3 0
3 years ago
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Nutka1998 [239]
None I mean you have to take a drivers test but you will have to take the knowldege test twice

4 0
4 years ago
Why does a projectile fired along a horizontal not follow a straight path?​
Stella [2.4K]

Answer: A projectile which is fired horizontally is being constantly acted upon by acceleration due to gravity, acting vertically downwards. Hence, it does not follow a straight line path. Also Why a projectile fixed along the horizontal not follow a straight line path? Because the projectile fired horizontally is constantly acts upon by acceleration due to gravity acting vertically downwards.

Explanation:

Hope this helped :)

3 0
3 years ago
An electron is in motion at 4.0 × 106 m/s horizontally when it enters a region of space between two parallel plates, as shown, s
max2010maxim [7]

Answer:

xmax = 9.5cm

Explanation:

In this case, the trajectory described by the electron, when it enters in the region between the parallel plates, is a semi parabolic trajectory.

In order to find the horizontal distance traveled by the electron you first calculate the vertical acceleration of the electron.

You use the Newton second law and the electric force on the electron:

F_e=qE=ma             (1)

q: charge of the electron = 1.6*10^-19 C

m: mass of the electron = 9.1*10-31 kg

E: magnitude of the electric field = 4.0*10^2N/C

You solve the equation (1) for a:

a=\frac{qE}{m}=\frac{(1.6*10^{-19}C)(4.0*10^2N/C)}{9.1*10^{-31}kg}=7.03*10^{13}\frac{m}{s^2}

Next, you use the following formula for the maximum horizontal distance reached by an object, with semi parabolic motion at a height of d:

x_{max}=v_o\sqrt{\frac{2d}{a}}             (2)

Here, the height d is the distance between the plates d = 2.0cm = 0.02m

vo: initial velocity of the electron = 4.0*10^6m/s

You replace the values of the parameters in the equation (2):

x_{max}=(4.0*10^6m/s)\sqrt{\frac{2(0.02m)}{7.03*10^{13}m/s^2}}\\\\x_{max}=0.095m=9.5cm

The horizontal distance traveled by the electron is 9.5cm

4 0
3 years ago
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