What are the equations and steps to solve these two problems?

In summary: Essentially, you need to find the acceleration in both problems by using the given equations and the unknown variables. For the first problem, you can use the equation F=ma and solve for acceleration by dividing the friction force by the mass of the bat. This will give you the minimum acceleration needed for the bat to stay in place.For the second problem, you can use the equation F=ma again, but this time the force will be the component of weight down the ramp, which you can find using trigonometry. Set this equal to the friction force and solve for the coefficient of friction.Remember to always start by setting up your equations with variables and then substituting in values. And don't forget to consider the 30 degree angle in
  • #1
da5id2
3
0
I have two separate problems that I think require essentially the same equations and thought process. So if I can get one I should be able to get the other:

First problem

Homework Statement


A bat crashes into the vertical front of an accelerating subway train. If the coefficient of friction between bat and train is 0.89, what is the minimum acceleration of the train that will allow the bat to remain in place?

Homework Equations


Friction=[mu]*N
F=ma
kinematics equations
?

The Attempt at a Solution


No idea how to even start this one.


Second problem

Homework Statement


At the end of a factory production line, boxes start from rest and slide down a 30 degree ramp 5.7 m long. If the slide is to take no more than 3.5 s, what is the maximum allowed frictional coefficient?

Homework Equations


same as first problem, i think?

The Attempt at a Solution


First I thought that I need to find the acceleration of the box over 5.7 meters in 3.5 seconds. I got about .931 m/s^2. I'm not sure where to go from there. One big question I have is how does the 30 degree angle play into the question?

Thanks!
 
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  • #2
In both of these situations, it would probably be helpful to draw a free body diagram for the bat in #1 and for the box in #2. Then use the equations that you have identified.

Also, You will find it helpful to set up and manipulate your equations with variables first before trying to substitue in any values. You will discover some things you think you need to know will divide out of the equations...
 
  • #3
Galileo's Ghost said:
In both of these situations, it would probably be helpful to draw a free body diagram for the bat in #1 and for the box in #2. Then use the equations that you have identified.

Also, You will find it helpful to set up and manipulate your equations with variables first before trying to substitue in any values. You will discover some things you think you need to know will divide out of the equations...

Thanks for the reply. I drew the free body diagrams but I'm still not sure what to do and how to manipulate Newton's law.
 

FAQ: What are the equations and steps to solve these two problems?

What are Newton's Laws with Friction?

Newton's Laws with Friction are a set of three physical laws that describe the relationship between an object's motion and the forces acting upon it in the presence of friction. These laws were developed by Sir Isaac Newton and are fundamental principles in the study of classical mechanics.

What is the first law of motion with friction?

The first law, also known as the Law of Inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an external force. In the presence of friction, this law also takes into account the opposing force of friction that acts to slow down or stop an object's motion.

How does friction affect the second law of motion?

The second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. With friction, the force of friction acts in the opposite direction of the object's motion, reducing its acceleration and overall velocity.

What is the third law of motion with friction?

The third law, also known as the Law of Action and Reaction, states that for every action, there is an equal and opposite reaction. With friction, the object exerts a force on the surface it is in contact with, and the surface exerts an equal and opposite force on the object, known as the force of friction.

How is friction calculated in relation to Newton's Laws?

The force of friction can be calculated using the coefficient of friction, which is a measure of the roughness of two surfaces in contact. It is multiplied by the normal force, which is the force exerted by the surface on the object, to determine the force of friction acting on the object. This force is then taken into account when applying Newton's Laws to calculate an object's motion.

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