question_answer

On the horizontal surface of a truck, a block of mass 1 kg is placed \[(\mu =0.6)\] and truck is moving with acceleration \[\text{5}\,\text{m/}{{\text{s}}^{\text{2}}}\text{.}\] The frictional force acting on the block will be:\[(g=10\,m/{{s}^{2}})\]

A)  6 N            

B)  5.88 N

C)  7 N            

D)  9 N

Correct Answer: A

Solution :

 The frictional force acting on the block \[f=\mu R\] but from figure, \[R=mg\] \[f=\mu \,m\,g\] Here, \[\mu =0.6,\,m=1\,kg,\,g=10\,m/{{s}^{2}}\] \[\therefore \] \[f=0.6\times 1\times 10\,=6N\] Note: Due to acceleration of truck, the block experiences a forward force \[F=ma=1\times 5=5N\] Since \[f>F,\] so block is not displaced from its previous position.