In the figure,a force F is being applied to the block with a magnitude such that it moves up along the frictionless inclined place with a constant velocity of 5 m/s.The angle in the figure is 30 $\circ$ ,and the mass of the block is 50 kg.What is the normal force exerted by the inclined plane on the block (within 5% accuracy)?
A)50 N
B)240 N
C)425 N
D)500 N
E)zero

Question

In the figure,a force F is being applied to the block with a magnitude such that it moves up along the frictionless inclined place with a constant velocity of 5 m/s.The angle in the figure is 30 $\circ$ ,and the mass of the block is 50 kg.What is the normal force exerted by the inclined plane on the block (within 5% accuracy)? 
A)50 N 
B)240 N 
C)425 N 
D)500 N 
E)zero

Quizplus · Accepted Answer

Since the block is moving up with a constant velocity, the net force on the block must be zero. Therefore, the force of gravity acting downwards must be balanced by the component of the normal force acting upwards, which is equal to mgcos30°. 
mgcos30° = (50 kg)(9.8 m/s^2)(cos30°) = 425 N (rounded to nearest 5%)

In the Figure,a Force F Is Being Applied to the Block