Another Newton's Law Question.

In summary, the conversation discusses the calculation of the mass of a block being pulled with a constant velocity by a 50N force at an angle of 37 degrees above the horizontal. The answer in the book is 23.4kg, but one person got 20.3kg and another got 23.5kg. The difference is due to the inclusion of the normal force and the angle of the applied force. The equations of equilibrium can be used to solve for the mass. The conversation also mentions that the textbook may not clearly explain the effect of the normal force in this scenario.
  • #1
scan
23
0
Question: A force of 50N acting at 37degrees above the horizontal pulss a block along the floor with constant velocity. If the coefficient of friction between the blocck and the floor is 0.2, what is the mass of the block?

the answer in the book is 23.4kg

but when I did it I got 20.3kg.

my friend did it and he got 23.4kg but when I use his calcutions and calculated out I get 23.5kg.

He says you have to take the Normal force and substract 50sin37 because its being pulled along that direction. I say do you don't.

Help?
 
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  • #2
scan said:
the answer in the book is 23.4kg
That is correct.
He says you have to take the Normal force and substract 50sin37 because its being pulled along that direction. I say do you don't.
The fact that the 50N force is applied at angle will definitely affect the normal force. Write down the equilibrium equations for both horizontal and vertical components. Combine the two equations and you can solve for the mass.
 
  • #3
oh ok. that makes sense now. its just the textbook is so bad that it doesnt' say that the normal force can be affected.
 

Related to Another Newton's Law Question.

1. What is Newton's Third Law of Motion?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.

2. How does Newton's Third Law apply to real-life situations?

Newton's Third Law can be observed in many real-life situations, such as when we walk. When we take a step forward, our foot exerts a force on the ground which causes the ground to push back on our foot, propelling us forward. Another example is when a balloon is inflated, the air inside exerts a force on the walls of the balloon, and the walls push back, creating the balloon's shape.

3. Is there an exception to Newton's Third Law?

No, there is no exception to Newton's Third Law. It applies to all objects and forces, whether they are in motion or at rest. It is a fundamental principle of physics and has been proven to be true in countless experiments and observations.

4. How is Newton's Third Law related to the other laws of motion?

Newton's Third Law is related to the other two laws of motion in that it helps explain the concept of forces and how they affect the motion of objects. The First Law states that an object at rest will stay at rest unless acted upon by an external force, while the Second Law explains how force, mass, and acceleration are related. Newton's Third Law builds on these ideas by showing that forces always occur in pairs and have equal magnitudes and opposite directions.

5. Can Newton's Third Law be used to explain the motion of celestial bodies?

Yes, Newton's Third Law can be used to explain the motion of celestial bodies, such as planets orbiting around the sun. The gravitational force between the two objects is an example of action and reaction. The sun exerts a force on the planet, causing it to orbit, while the planet also exerts a force on the sun in the opposite direction. This is known as the Law of Universal Gravitation and is a direct application of Newton's Third Law.

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