How do I solve this physics problem of mechanics and Newton's laws?

In summary, the conversation discusses the concept of static and kinetic friction and how it relates to solving physics problems. The individuals are discussing the set up of a free body diagram for a large mass M and the forces involved in the static and kinetic states. One person is seeking clarification on the difference between the forces needed to overcome static and kinetic friction. They also mention being stuck on question 2 and question 1.
  • #1
mayalevy2
2
0
Homework Statement
Mass M and mass m connected by rope and pulley. The kinetic friction coefficient between mass M and table is 0.2 and the coefficient of static friction between them is 0.25.
M = 3kg, m = 1kg.
Force F is applied on mass M directed at a 30-degree angle above the table surface.

1. Will the system slide to the left if Force F is removed?
2. Calculate the minimum value of force F that will prevent the system from sliding.
3. Can the system slide to the right without F being applied?
4. Calculate the minimum value of Force F that will allow the system to swipe right.
5. What is the minimum value of Force F that will allow the system to keep the system moving at a constant speed?
6. Why are the answers to questions 4 and 5 not the same?
Relevant Equations
1. Yes
2. 3.37N
3. No
4. 17.7N
5. 16.6N
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  • #2
Please show what you've attempted so far. You should set up a free body diagram on the large mass M, showing all forces in the static state. Remember that static friction is the amount just enough to keep from moving up to the maximum available.

So are you just asking why 4 and 5 are different situations? Think about the force necessary to overcome static friction and the force necessary to overcome kinetic friction.
 
  • #3
Hey, I actually got stuck on Question 2 already, and I'm not sure if I solved Question 1 correctly either. I would love to see if you can help me. Here's what I've done so far:
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1. What are the steps to solve a physics problem involving mechanics and Newton's laws?

The steps to solving a physics problem using mechanics and Newton's laws are as follows:1. Identify the problem and gather all given information.2. Draw a diagram of the problem and label all known and unknown variables.3. Determine which laws of motion apply to the problem.4. Write out the equations corresponding to the laws of motion.5. Substitute the given values into the equations.6. Solve for the unknown variable.7. Check your answer to ensure it makes sense in the context of the problem.

2. How do I know which laws of motion to use in a physics problem?

To determine which laws of motion to use in a physics problem, you must first identify the type of motion involved. If the problem involves an object at rest or moving at a constant velocity, Newton's first law applies. If the problem involves an object experiencing acceleration, Newton's second law applies. If the problem involves forces acting on an object, Newton's third law applies.

3. What is the difference between mass and weight in physics?

Mass is a measure of the amount of matter in an object and is measured in kilograms (kg). Weight is a measure of the force exerted on an object due to gravity and is measured in Newtons (N). Mass remains constant regardless of the location, while weight changes depending on the strength of the gravitational field.

4. How do I calculate net force in a physics problem?

To calculate net force, you must first identify all the forces acting on an object and their directions (positive or negative). Then, using Newton's second law (F = ma), you can add all the forces together (taking into account their directions) to find the net force acting on the object. The net force will determine the acceleration of the object according to the equation a = F/m.

5. How do I approach a physics problem that involves multiple objects?

When solving a physics problem involving multiple objects, it is important to first draw a separate free-body diagram for each object. This will help you identify all the forces acting on each object and their directions. Then, you can apply Newton's second law (F = ma) to each object individually, taking into account the net force acting on each object and their respective masses. Finally, you can use the equations of motion to solve for any unknown variables for each object.

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