A 75 kg box slides down a 25.0 degree ramp with an acceleration of 3.60 m/s^2.
Find coefficient between the box and the ramp. What acceleration would a 175 kg box have on this ramp?

Respuesta :

Answer:

The coefficient and acceleration are 0.061 and 8.284 m/s².

Explanation:

Given that,

Mass = 75 kg

Angle = 25.0°

Acceleration = 3.60 m/s²

We need to find the force

[tex]F=ma[/tex]

[tex]F=75\times3.60[/tex]

[tex]F=270\ N[/tex]

Now, we need to calculate the parallel force

[tex]F'=mg\sin\theta[/tex]

[tex]F'=75\times9.8\times\sin25^{\circ}[/tex]

[tex]F'=310.62\ N[/tex]

We calculate the friction force

[tex]f_{\mu}=F'-F[/tex]

[tex]f_{\mu}=310.6-270[/tex]

[tex]f_{mu}=40.6\ N=approx 41\ N[/tex]

If the box is moving in an angle, then the weight

[tex]W = mg\ \cos\theta[/tex]

If it is horizontally then

[tex]W = mg[/tex]

So, The normal force is

[tex]F'' = 75\times9.8\times\cos25^{\circ}[/tex]

[tex]F''= 666.13\ N[/tex]

We need to calculate the coefficient between the box and ramp

[tex]f_{\mu}=\mu\times F''[/tex]

Where, [tex]\mu[/tex]=friction coefficient

[tex]f_{\mu}[/tex]=frictional force

F''=normal force

Put the value into the formula

[tex]\mu=\dfrac{f_{\mu}}{F''}[/tex]

[tex]\mu=\dfrac{41}{666.13}[/tex]

[tex]\mu=0.061[/tex]

We need to calculate the acceleration

[tex]F''-f_{\mu}=ma[/tex]

[tex]mg\cos25^{\circ}-\mu mg=ma[/tex]

[tex]175\times9.8\cos25.0^{\circ}-0.061\times175\times9.8=175\times a[/tex]

[tex]a=\dfrac{175\times9.8\cos25.0^{\circ}-0.061\times175\times9.8}{175}[/tex]

[tex]a=8.284\ m/s^2[/tex]

Hence, The coefficient and acceleration are 0.061 and 8.284 m/s².

The coefficient of friction is 0.14 and the acceleration of the 175 Kg box is 2.95 m/s^2.

We know that;

ma = -Ff + mgsinθ

Ff = frictional force on the box

But Ff = μmgcosθ

Hence;

ma =  mgsinθ - μmgcosθ

μmgcosθ = mgsinθ - ma

μ = mgsinθ - ma/mgcosθ

Substituting values;

m = 75 kg

a = 3.60 m/s^2

θ = 25.0°

μ =[tex][75 kg * 10 m/s^2 (sin 25.0)] - [75 kg * 3.60 m/s^2]/[75 kg * 10 m/s^2 (cos 25.0)][/tex]

μ = 316.96 N - 225 N/679.73

μ = 91.96/679.73

μ = 0.14

From μmgcosθ = mgsinθ - ma

a = mgsinθ -  μmgcosθ /m

a =[tex][175 kg * 10 m/s^2 (sin 25.0)] - [0.14 * 175 kg * 10 m/s^2* (cos 25.0)]/175Kg[/tex]

a = 739.58 - 222.05/175

a = 2.95 m/s^2

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