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Problem 38 Easy Difficulty

A 35-kg crate rests on a horizontal floor, and a 65-kg person is standing on the crate. Determine the magnitude of the normal force that (a) the floor exerts on the crate and (b) the crate exerts on the person.

Answer

980$N$
640$N$

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Video Transcript

we begin this question by drawing the force that are acting on our system so the gravitational force acts on the crate. Then there is a force that before exerts on the crate, acting on that great at the same time, they would have additional forced acts on the person, and then the great exerts some force on that person. So these are the forces that are acting on our problem. Then, to solve the problem, we have to apply Newton second low. So first, let's apply Newton's second law the crate. So the net force acting on the great is equals to the mass off the crate Times declaration off the creed note that the crate is a standing still, so it's not moving. Their foreign declaration is close to zero. That which was my referential has being that everything that is pointing up its positive on everything that is pointing down is negative. In this attempt, the Net force acting on the great eggs equals two miners the weight off the create, plus the force that the floor exerts on the great minus force that the person exerts on the crate, which is equals to the weight force off this person. Serve my nose. The weight off the person on this is a question zero. Therefore, the force that's the floor exerts on the crate is a close to the weight off the great, plus the weight off the person. And these is equals truth. The mass off the crate times acceleration off gravity plus the mass off the person times Next operation off gravity. So considering that declaration off gravity is equals to approximately 9.8 meters per second squared, we get that The force that the floor exerts on the great is equals to 35 times 9.8 plus 65. Thanks 9.8. These results in the force exerted by the floor on the crate off 980 Newtons. This is the force that the floor exerts on the great. Now we apply Newton's second law to the person. So no a plane to the person we got the following than that force that is acting on the person. Is it close to zero because the person is a standing steel, so it's extra relation. Is it close to zero because it's so so not going to move and there are two forces acting on the person. One force is the force that the create exerts on the person, and the other is the weight off the person, which is negative because of my choice of referential New Jersey close to zero. Therefore, the force that decreed exerts on the person is a close to the weight off the person that is given by the mass off the person times the acceleration of gravity, which is equals to 65 times 9.8. And these gives us a force that the crate exerts on the person off 600 on 37 Newton.