A boy is cycling such that the wheel of the cycle are making 420 revolutions per minute. If the diam

Dr.Dipin Singh   11 years AGO

speed of the boy = 2*(22/7)*0.25*420*60/(1000)= 39.6 km/hr

Like? Yes (9) | No (5)  

ShAg   11 years AGO

420 rev per minute = 7 rev per sec
distance covered in 1 rev = circumference of wheel
circumference of wheel = (22/7)*50 cm
so distance covered in 1 sec = (22/7)*50*7 = 1100 cm
so speed = 11 m/s = 39.6 km/hr

Like? Yes (5) | No (2)  

KALIDASS   11 years AGO

D=50*10^-2 m
N=420 RPM
SPEED=3.14*D*N/60
=3.14*50*10^-2*420/(60)=10.99 m/s=39.58 km/hr

Like? Yes (6) | No (4)  

Deepak Sharma   11 years AGO

Speed of wheel=420revolution per min.
=25200revolution per hr.
Dia. of wheel = 50cm=0.0005 km
so distence coverd in 1 resolution=circumfrence of wheel =0.0005*22/7
so speed of the boy = 0.0005*22/7*25200 km/hr.
=39.6 km/hr
so the option 8 is correct.

Like? Yes (4) | No (3)  

Hardik Dungrani   11 years AGO

diameter is 50 cm.. so 3.14*50=157 cm
3.14*.5=1.57
cycle making 420 revolution so..
(3.14*.5*420*60(for hours))/1000(km)=39.564=39.6 km/hr

Like? Yes (2) | No (1)  

Yallapu Uday tarun kumar   11 years AGO

circumference c=2*22*25/7 cms
per min rotations distance=420*c cms
per hour=420*c*60 cms
speed=420*c*60/(100*1000)=39.6km/hr

Like? Yes (4) | No (3)  

Rashmi bharti   11 years AGO

Circumference=3.14 *0.5=1.57m;
RPM= 420rpm;
Linear Speed =Circumference*420rpm=659.4m/min
Linear Speed in km/h =659.4*60/1000=39.6 km/h

Like? Yes (4) | No (4)  

ANTO PRAVIN   11 years AGO

speed=3.14*d*n/60
d=0.5 m
s=(3.14*.5*420)/60=10.99 m/s
=10.99*18/5=39.569 km/hr

ANS:39.6 km/hr

Like? Yes (2) | No (3)  

GOKULVASANTH   11 years AGO

speed=3.14*d*n/60
=39.56

Like? Yes (2) | No (3)  

Jasmine Khan   11 years AGO

1 min=420 rounds
1/7 sec=1 round=circumference of the wheel
radius=0.25 m
speed=distance/time
speed=[2*(pi)*r]/(1/7)
speed=14*22/7*0.25
speed=11 m/sec
speed=11*3600/1000 km/hr
speed=36.9 km/hr

Like? Yes (1) | No (2)  

Amit Gupta   11 years AGO

radius of wheel=50/2=25cm
perimeter of wheel =2*pi*r=2*(22/7)*25=157.34
then 1 revolution=157.34cm
420 revolutions=157.34*420=66000cm
that is 1 minute=66000 cm
1 hour =(66000*60)/(100*1000)=39.6km/hr.

Like? Yes (1) | No (2)  

usha devi   11 years AGO

perimeter of the wheel=50*22/7
for 420 revolutions it must have covered 420*50*22/7cm=66000cm=660m/min=11m/s
11*18/5=39.6km/hr

Like? Yes (2) | No (3)  

Anantharaman   11 years AGO

Bicycle speed calculation is based on circumference of wheel and RPM

RPM = 420/min = (420*60)/hr

circumference = π * d

d=50 cm = 0.5m

circumference = 3.142 * 0.5 as (π = 3.142)

speed = 3.142 * 0.5 * 420 * 60 = 39589.2 m/hr

Convert into KM => 39.5892 km/hr

approx => 39.6 km/hr

Like? Yes (2) | No (3)  

krishnapriya   11 years AGO

Given 420 revolutions/min and diameter 50cm
Dis. travelled in a minute=420*pi*50
Dis. travelled in an hour=420*pi*50*60 cm
=420*pi*5*6m
=0.42*pi*5*6 km
=39.6 km/hr

Like? Yes (1) | No (2)  

hcair   11 years AGO

420 revolution per minute.
420/60 = 7 ---> revolution per second.
circumference of circle is= 3.14*50=157 cm
speed of boy = 157*7 cm/s
= 10.99 m/s
= 10.99*(18/5)km/hr
= 39.564 km/hr

Like? Yes (1) | No (2)  

ch.jyothsna   11 years AGO

radius=50/2=25
distance covered=2*(3.14)*25=157 cm = 1.57 m
revolutions per sec= 420/60=7
time taken for 1 revolution= 1/7=0.14285 sec
speed= distance/time= 1.57/0.14285=10.99 m/sec = 39.6 km/hr

Like? Yes (1) | No (2)  

TCS 2014   11 years AGO

1sec 7 revolution
speed=22*50/7=1100cm/s=1100*18/5km/h=39.6km/h

Like? Yes (1) | No (2)  

vaibhav rajhns   11 years AGO

total distance=3.14*.5*420/1000 km
time=1/60 hr
speed=distance/time
=39.564km/hr

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devendra kumar gond   11 years AGO

speed of the boy =rpm*circumference/60

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Suman Saurabh   11 years AGO

Distance travelled in one revolution = 3.14*50=157 cm
total distance travelled in 420 revolutions = 420*157=65940 cm
speed=65940/60*100=10.99 m/s = 10.99 *(18/5) km/hr = 39.564 km/hr

so option 8 is right answer.

Like? Yes (3) | No (4)  

Arpit Srivastava   11 years AGO

420 rev per min= 7 rev per sec.
50cm= 1/2 m
radius= 1/4 m
circumfrence= 2X(22/7)X(1/4)
= 11/7 m
distance= 11/7 m
speed= (11/7)*7 m/sec
=39.6 km/hr

Like? Yes (1) | No (2)  

Akshay Kumar Singh   11 years AGO

wheel perimeter=2*(3.14)*(50/2);
=157.0cm
total distance per minute=420*157=65940 cm;
=659.4 m;
=659.4*(18/5)km/hr;
=39.6 km/hr;

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Sneha Agarwal   11 years AGO

speed = distance/time
= 420*2*pi*r/1min

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Abhijeet Kumar   11 years AGO

Distance travel in 1 min
= 420*(pi*d)=420*(3.14*50)=65940 cm
Now Distance travel in 1hr is
= 60*65940 = 3956400 cm =39.56 km
speed = 39.56 km/hr = 39.6 km/hr

Like? Yes (1) | No (2)  

Jacky shevkani   11 years AGO

as the diameter of the wheel is 50 cm

therefore the circumference of that wheel will be
pi * d
that is 3.14 * 50=157 cm .

therefore the distance covered per revolution is 157 cm .
as the wheel is making 420 revolution per minute .
therefore the distance covered per minute will be 157*420=65940cm.

therefore speed is 65940cm per minute
converting into km per hour we get
speed=39.6km per hour.

Like? Yes (1) | No (2)  

richa ahuja   11 years AGO

diam=50cm
thus radius=25cm=25*10^-5km
1 revolution=157.14286*10^-5km
420 revolution=420*157.14284*10^-5=66000*10^-5=0.66
speed=distance/time=0.66*60km/hr=39.6km/hr

Like? Yes (1) | No (2)  

Kunal Verma   11 years AGO

c=2*22/7*25 = 157 cm
total distance= 420*157=65940in cms =65940/100000=0.65940km/mins=0.6594*60 hrs= 39.6km/hr

Like? Yes (3) | No (4)  

k.v.s.nayana   11 years AGO

given N=420rpm
dia D=.5 m
we hav w=(2*3.14*420)/60
speed v=w*(D/2)

Like? Yes (2) | No (3)  

ravi singh   11 years AGO

amswer is 39.6km/hr

given that frequency
f = 420 revolution per minute

therefore time t=1/f= 1/420 min

and since diameter is 50 cm hence distance

D =perimeter= (22/7)*50 cm

hence speed
S= D/t=66000 cm/min
=> S=39.6 km/hr

hence option 8 is right answer

Like? Yes (1) | No (2)  

aamir alam   11 years AGO

in one revolution it travells =3.14*50=157
Distence travel in 420 revolution=420*157=65940
so speed of boy=65940*60/100000=39.6km/hr

Like? Yes (1) | No (2)  

ravinder singh   11 years AGO

since circumference =3.14*d(diameter)
in one revolution distance covered is=3.14*.50(meter)
so,in 420 revolution =(.50*3.14*420*60(for hour convertion))/1000(km)=39.564km/hr(approx)

Like? Yes (1) | No (2)  

saima kidwai   11 years AGO

total distance covered= 420*2*3.14*25*10^-2 m
(n*2*pi*r)
= 659.4 m
total time taken= 60sec
speed=659.4/60 m/s
=10.99 m/s
=10.99*18/5 km/hr
=39.6 km/hr

Like? Yes (4) | No (5)  

Anilkumar   11 years AGO

(420*0.5*3.14*60)/1000=39.564

Like? Yes (1) | No (2)  

Balakumaran N.A   11 years AGO

since circumference =3.14*d(diameter)
in one revolution distance covered is=3.14*.50(meter)
so,in 420 revolution =(.50*3.14*420*60(for hour convertion))/1000(km)=39.564km/hr

Like? Yes (2) | No (3)  

smith kumar saha   11 years AGO

since circumference =3.14*d(diameter)
in one revolution distance covered is=3.14*.50(meter)
so,in 420 revolution =(.50*3.14*420*60(for hour convertion))/1000(km)=39.564km/hr

Like? Yes (1) | No (2)  

ponprakash   11 years AGO

8)39.6 km/h
3.14=x
420*50=21000xcm/m
21000*60 min/100m*1000min
=12600xkm/h
i.e- 39.6 km/hr

Like? Yes (1) | No (2)  

prakash kumar   11 years AGO

distance covered after 420 rev=22/7*50*420
=66000cm/min
=0.66km/min
=0.66*60km/h
=39.6km/h

Like? Yes (1) | No (2)  

ravi chandra singh   11 years AGO

since,
1 revolution give 2*pie*r meter=2*3.14*25/100
=1.57 m

so, 420 revolution give 1.57*420/1000=.6594 km


so, required speed=.6594*60=39.564=39.6Km/hr

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Tanu   11 years AGO

d=420*2* pie*r;
s=d/t;

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praveen sb   11 years AGO

8 is the answer....for one revolution of the wheel the distance is PI*diameer = 50*3.142
therefore total speed is 420*60*50*3.142=3960000 cm/hr roughly calculated value.... if v convert this into km/hr we get 39.6 km/hr......

Like? Yes (1) | No (3)  

Rahul Kumar Mehta   11 years AGO

Diameter = 50 cm then radius(r) = 50/2 cm

AS answer is given in (km) we have to convert (cm) in (km).
Now r= 50/2= 25 cm then (25/100) in meter then (25/100*1000) in km

Circumference of cycle = 2*22/7*r

Number of revolutions per minute = 420

we have to multiply 60 with circumference becoz it will be converted into hour as answer is given in hour only.

speed = 2*(22/7)*[25/(100*1000)]*60*420 km/hr
= 396/10 km/hr
= 39.6 km/hr

Like? Yes (2) | No (4)  

SOMASHEKAR MACHANI   11 years AGO

distance travelled per min = 420*3.142*.5/60 m/s
speed=10.997 m/s
speed= 10.997*(18/5) km/hr
speed=39.589=39.6 km/hr

Like? Yes (2) | No (4)  

Anil Kumar Bharti   11 years AGO

Exp:
perimeter of wheel=(22/7)*50 cm
Rev in 1min=420 then in 1sec=420/60=7

So distance in 1sec={(22/7)*50*7}/100=11 Meter
Hence in KM =11*18/5=39.6 KM/hr Ans

Like? Yes (2) | No (4)  

ABHISHEK KUMAR MISHRA   11 years AGO

in one revolution it will take (22/7)*50 cm also in one minute it will take 420*(22/7)*50 cm
so in one hour it will be 420*(22/7)*50*60 cm
so according to option [420*(22/7)*50*60]/100000 km/hr = 39.6 km/hr ans

Like? Yes (2) | No (4)  

Kumar Ankit   11 years AGO

Given:420 revolution in 60 sec and 2r=50cm i.e 0.5m
hence 1 revolution in 60/420 sec i.e
distance traveled in 60 sec=2r*3.14
0.5*3.14

Speed=distance/time
3.14*0.5*420/60=10.99 m/sec
hence 10.99*18/5=39.6km/hr

Like? Yes (1) | No (3)  

Shuvankar Ghosh   11 years AGO

(50*3.14*60*420)/(100000)=39.56

Like? Yes (1) | No (3)  

Devendra Marghade   11 years AGO

Given Diameter=50 cm so Radius=25 cm.
Distance covered in one revolution=2*Pi*25=50*Pi cm
For 420 revolutions distance covered=420*50*Pi cm =66000 cm/min
=66000*60/100000 km/hr
=39.6 km/hr

Like? Yes (2) | No (5)