A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in the figure.The 6.00-kg block is being pushed by a horizontal force as shown.What is the magnitude of the force that the block exerts on the block?
A) 6.00 N
B) 20.0 N
C) 8.00 N
D) 4.00 N
E) 10.0 N

Question

A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in the figure.The 6.00-kg block is being pushed by a horizontal  force as shown.What is the magnitude of the force that the  block exerts on the  block? 
A) 6.00 N 
B) 20.0 N 
C) 8.00 N 
D) 4.00 N 
E) 10.0 N

Quizplus · Accepted Answer

As the surface is frictionless, the net force acting on both the blocks is equal to the push force applied on the 6.00-kg block, which is 11.0 N. According to Newton's third law, the force that the 6.00-kg block exerts on the 4.00-kg block is equal in magnitude and opposite in direction to the force that the 4.00-kg block exerts on the 6.00-kg block. Therefore, the magnitude of the force that the 4.00-kg block exerts on the 6.00-kg block is also 11 N. However, the question asks for the magnitude of the force that the 11ea83ea_6976_cae4_aeff_e308bf667c97_TB6394_11 block exerts on the 11ea83ea_6976_f1f5_aeff_45e847bbab30_TB6394_11 block, which is the magnitude of the force that the 4.00-kg block exerts on the 6.00-kg block, i.e., 11.0 N. Therefore, the best choice is C).

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