Pumping rubber

One can work out by either lifting weights or using a tension band, which is like a big rubber band. If we model the rubber band as a big spring with spring constant 400 N/m 400~\mbox{N/m} , how far in meters must I stretch the the band so it applies a force equivalent to the gravitational force on a 10 kg 10~\mbox{kg} weight?

Details and assumptions

  • The acceleration of gravity is 9.8 m/s 2 -9.8~\mbox{m/s}^2 .


The answer is 0.245.

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12 solutions

Ronan Laker
Oct 21, 2013

To solve this problem you must use Hooke's law F=kx where k is spring constant (400N/m) and x is to be found. We can work out the force by using f=ma, so 10*9.8=98N. Re-arrange the first equation to get F/k=x so 98/400=0.245m

plz send me more information about hooke's law( a pdf if possible) on my email -> [email protected] and I am in 10th grade so plz use language simple so that i can understand easily.

Ayush Porwal - 7 years, 7 months ago

spring constant=force/elongation; k=f/e; k=mg/e; 400=10*9.8/e; e=98/400; e=0.245

Karan Singh
Oct 20, 2013

If we pull the rubber band through a distance of x x metres , the restoring force produced = k x -kx , where k k is the spring constant . By the given condition , k x = m g -kx=mg . Therefore , x = m g k x=\frac{-mg}{k} . Substituting m = 10 k g m=10kg , k = 400 N / m k=400N/m and g = 9.8 m / s 2 g=-9.8m/s^2 , we get x = 0.245 x=0.245 m .

Andi M
Mar 6, 2014

F = k . x F=k.x so, x = F k x=\frac{F}{k} x = 9.8 x 10 400 = 0.245 m e t e r s x=\frac{9.8x10}{400} = 0.245 meters

HERE mg=kx..so x=mg/k=10*9.8/400=.245

Sunil Jadhav
Jan 17, 2014

the gravity on 10kg mass is 98N 400 N/m /98 N =0.245

Nahom Yemane
Jan 3, 2014

F = k x F=kx where F F is F o r c e Force , k k is S p r i n g Spring C o n s t a n t Constant and x x is d i s t a n c e distance

F = 10 9.8 = 98 F=10*9.8=98 and k = 400 k=400

98 = 400 x 98=400x

x = 98 400 = 0.245 x=\frac{98}{400}=\boxed{0.245}

Muhammad Mustafa
Dec 26, 2013

spring force formula is : F=kx where k is the spring constant and x is the compression distance spring force also equal to gravitational force on a 10 kg weight ( given)

i.e. F= 10* 9.8 = 98 N

then X= F/K = 98/400 = 0.245 m

Budi Utomo
Dec 24, 2013

F/s = E ---> mg/h = E ---> 10 x 9,8 / s = 400 ----> s = 98/400 = 0.245. Answer : 2.45E-1

Varuni Jayakody
Oct 24, 2013

Force=-(force constant)(distance) Hooke's Law

Therefore, distance=-(10 kg x -9.8 ms-2)/ (400 kgms-2) =0.245 m

Ayon Pal
Oct 23, 2013

I must stretch the band so it applies a force equivalent to the gravitational force on a 10 kg weight is:

10 9.8 400 \implies \frac{10 * 9.8}{400}

98 400 0.245 m e t e r s \implies \frac{98}{400} \implies \boxed{0.245 meters}

Anyone watch that there is two "the" in the Middle of the Question?

F=kx=W=mg W=10[9.8]=400x Hence,x=0.245m

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