MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM

DETAILS

MRP

DISCOUNT

FINAL PRICE

Total Price: Rs.

There are no items in this cart.

Continue Shopping

Continue Shopping

Menu

` `A particle moving in a straight line covers half the distance with speed of 3m/s. The other half of the distance is covered in two equal time intervals with speed of 4.5 m/s and 7.5 m/s respectively. The average speed of the particle during this motion is?

6 years ago

Let total distance=d

Total time=T

Then in d/2.......

t1=d/6

t2=d/(4*4.5) + d/(4*7.5)

=4d/45

T=t1+t2=d/6+4d/45 =23d/90

Average speed =t. Dis/t. Time= d/T =3.91

m/s........ANS

All the best!!!!!

6 years ago

let total distance of path is S ...

for first half , time taken if t

speed = distance/time

3 = S/2t

t = S/6 .............1

for second half , time taken is T ...

for first T/2 it moves with 4.5

speed = distance/time

4.5 = 2x/T

x = 4.5T/2 ...........2

for second T/2 it moves with 7.5

7.5 = 2y/T

y = 7.5T/2 ..........3

we have , x+y = S/2so

(7.5+4.5)T = S/2

T = S/24 ...............4

total time taken during its motion is T+t

T

_{total}= T+t = S/24+S/6 = 5S/24total distance = S

average speed = total distance/total time = S/5S/24 = 24/5 = 4.8m/s

approve if u like my ans

6 years ago

hi

let the distanc covered with speed 3m/s be x.mts

time taken is x/3sec.

ii)second half(x mts)

time taken to travel second half will be 18x/11.25 sec

avg. speed=total distanc /totaltime

avg.speed=1.9m/s

plzz. prove!!!!!!!!!!!!!!!!!!!!!!!!!!

6 years ago

Let total distance be S. Total time be T and V1= 3m/s be the velocity for which it covers the first half of the distance and V2 = 4.5 m/s and V3 = 7.5 m/s be the velocities in the second half of the distance. Let <v> be the average velocity that has to be calculated.

Let the other half be completed in times t1 and t2 (t1= t2=t, from the question).

For Ist half of the distance:

S/2= V1(T-2t)

=> T = S/2V1 + 2t ....(1)

For 2nd half of the distance:

S/2 = (V2 + V3)2t

=> S = 4(V2 + V3)t ....(2)

From (1) and (2).

T = {2(V2 + V3)/V1 + 2}t ....(3)

we know that,

<v> = total distance/total time

so,

<v> = S/T

Putting the values of T and S from (3) and (2),

<v> = 4(V2 + V2)t /{2(V2 + V3)/V1 +2 }t

=> <v> = 2V1 (V2 + V3)/(2V1 + V2 + V3)

putting the values of V1, V2 and V3.

<v> = 4 m/s.

6 years ago

all the answers are waste of timethere is a formulae 2v1*v2/v1+v2 if the particle travels in 2 equal time intervals so lets take second distance 4.5+7.5/2 =12m/s so 2*v_{1}*v_{2}/v_{1}+v_{2}= 2*3*6/6+3 =36/9=4.0 m/s

8 months ago

all the answers are waste of timethere is a formulae 2v1*v2/v1+v2 if the particle travels in 2 equal time intervals so lets take second distance 4.5+7.5/2 =12m/s so 2*v_{1}*v_{2}/v_{1}+v_{2}= 2*3*6/6+3 =36/9=4.0 m/sanswered by a 8^{th}grade

8 months ago

Avg.speed =total distance /total time taken Avg. Speed in 2nd half=(sT +ST)/2T = (4.5T+7.5T)/2T=6m/sTotal avg.Speed = D/(d/2)/3+(d/2)/6 =12D/3D=4m/s

one month ago

Think You Can Provide A **Better Answer ?**

Answer & Earn Cool Goodies

Have any Question? Ask Experts

Post Question

copyright © 2006-2017 askIITians.com

info@askiitians.com