Shuffleboard

Shuffleboard is a game played with wooden disks on a wooden surface. You give the disks an initial horizontal velocity and try to get them to stop at a certain point. A disk and the surface have a coefficient of kinetic friction equal to 0.1 0.1 . What is the initial velocity in m/s you must give the disk to have it stop 5 m 5~\mbox{m} away from its launch point?

Details and assumptions

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


The answer is 3.13.

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11 solutions

Mohamed A.B
Nov 18, 2013

using-work energy principle the work done by friction force=change in kinetic energy you will need to know:

R is the contact force, = mg

m mass of the disk,

u initial velocity,

v final velocity ,

now we can use the work energy principle to say 0.1 × m g × 5 = 0 1 2 × m × v 2 0.1 \times mg\times 5=0-\frac{1}{2} \times m \times v^{2} this can be simplified by cancelling the m out from both sides and getting 5 × 0.1 × 9.8 = 1 2 × v 2 5 \times 0.1 \times 9.8=\frac{1}{2} \times v^{2} v 2 = 9.8 v^{2}=9.8

THEN THE ANSWER IS v = 3.13 v=3.13

Isn't Work-Energy Principle: change in KE = Work Total = (summation of force)xdisplacement. Wouldn't the equation rather be: (F - f)d = 1/2mv^2, since there has to be an unknown force applied other than friction to move the disk. ??????

Reb Malaya Mejino - 7 years, 6 months ago

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no no no it's not necessary to have a constant applied force on the disk it's moving against friction so it's decelerating

mohamed A.B - 7 years, 6 months ago

Work Energy Theorem Can Only Be Applied When The Forces Acting On The System Are Conservative...!!!! And Friction IS A Non-Conservative Force...!!! Correct Process Is V²=U²-2as Where V=0 a=u g => a=.0.1 9.8 s=5m ==>> U=3.13

Ram Mohan Madhamanchi - 7 years, 6 months ago

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. . . are you yelling?

Reginald McNair - 7 years, 6 months ago

hmmm i dont get it so i cant apply work energy principle with friction force in the system!!!!! i would like you to recheck ur resources please

mohamed A.B - 7 years, 6 months ago

We know that the work done by friction of friction W f = F f × d = F n × μ × d W_f = F_f \times d\ = F_n \times \mu \times d on flat surfaces.
Also, the kinetic energy of an object is given by K E = 1 2 × m × v 2 KE = \frac{1}{2} \times m \times v^{2} .

In order to be at rest, the velocity must be zero, therefore work done by friction to slow the disk must be equal to the initial kinetic energy of the disk itself:
K E = W f KE= W_f
1 2 × m × v 2 = m × g × μ × d \frac{1}{2} \times m \times v^{2} = m\times g \times \mu \times d
After cancelling out the mass term on both sides and multiplying both sides by 2:
v 2 = 2 × 9.8 × 0.1 × 5 v^{2} = 2 \times 9.8 \times 0.1 \times 5
v = 9.8 = 3.13 v = \sqrt{9.8} = \boxed{3.13} which is the final answer.


what is mew?

Jeff Brown - 7 years, 3 months ago

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Its the coefficient of friction of the surface . Differs for different surfaces .

sankar ram - 6 years, 6 months ago
Abhijeeth Babu
Dec 24, 2013

Here the retarding force is equal to f k = μ k N = μ k m g f_k=-\mu_k N=-\mu_k mg . Let μ k m g = m a -\mu_k mg=ma , thus μ k g = a = v d v d x = -\mu_k g=a=v \dfrac{\mathrm dv}{\mathrm dx}= 0 x i μ k g d x = v i 0 \Rightarrow -\int_0^{x_i} \mu_k g \mathrm dx= \int_{v_i}^0 Thus μ k g ( x i ) = ( v i ) 2 2 \mu_k g\cdot (x_i)=\dfrac{(v_i)^2}{2} . Substituting the values x i = 5 m x_i=5m we obtain v i = 3.130 m s 1 v_i=3.130ms^{-1} .

Ali Ahmed
Jan 28, 2014

K.E = work done by non conservative force 1/2 mv^2= umgl so. v^2=(2ugl)^1/2 v^2=(2 x 0.1 x 9.8 x5) s.r. on both side v=√9.8 v= 3.1304951685

Swapnil Thigale
Jan 15, 2014

1/2mv^2=umgx.....KE lost due friction=work done by non conservative force, here x=5m

Sunil Jadhav
Jan 15, 2014

½ mv^2 = umgl so v = (2ugl)^1/2 v = (2 0.1 9.8*5) v = 3.1 m/s

Azizul Islam
Jan 12, 2014

0.1= ma/mg, a=0.98, u=(2x0.98x5)^0.5, =3.13

ma=0.1mg

a=-9.8m/s2

v2=u2+2as

v=0

a=3.130

Alan Li
Nov 22, 2013

Energy from friction is what stops the disk, we we find the work from friction

w=fd

w=MND

w=.1* m * 9.8*5

w=4.9m

Work is equivalent to mechanical energy, which is kinetic

4.9m=.5mv^2

Now we can conveniently cancel m from both sides

4.9=.5*v^2

9.8=v^2

3.13=v

this is the simplest methode beautiful piece of work

Juma Khan Zahidi - 7 years, 6 months ago
Gabriel Cruz
Nov 21, 2013

m = mass g = acceleration due to gravity N = normal force u = coefficient of kinetic friction d = distance

Newton's second law: net force = ma

Along the vertical, N = mg

Along the horizontal, -friction = ma -uN = ma -umg = ma --> a = -ug

From kinematic equations:

a = [(Vfinal)^2 - (Vinitial)^2]/2d

Since Vfinal = 0

--> v(initial) = sqrt(2ugd)

= 3.13 m/s

Samrit Pramanik
Nov 20, 2013
  1. v=0, s=5 m v2 = u2  2as 02 = u2  10a Now, the co-efficient of kinetic friction is μ f = μN = μmg = ma a = μg = 0.1 × 9.8 = 0.98 Now, u2  10a = 0 u2  10 × 0.98 = 0 u2 = 9.8 u = 3.13

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