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A delivery company has unloaded a 21 kg crate in your driveway. The coefficient of static friction between the crate and the driveway surface is μs = 0.70. The coefficient of kinetic friction is μk = 0.60. In order to move the crate, you apply a horizontal force of magnitude F by pushing on it. As a result, the crate slides with an acceleration of 4.0 m/s2. What is the force F?

Respuesta :

Answer:

F = 207.48 N

Explanation:

given,

mass of crate = 21 kg    

μs = 0.70        

μk = 0.60          

a = 4 m/s²      

normal reaction force      

N = m g        

[tex]F_{net}=F-f_k[/tex]      

[tex]F_{net}=F-\mu_k N[/tex]        

[tex]F_{net}=F-\mu_k mg[/tex]          

[tex]ma=F-\mu_k mg[/tex]          

[tex]F =m(a + \mu_k g)[/tex]      

[tex]F =21 (4 + 0.6 \times 9.8)[/tex]

F = 207.48 N

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