Forces and the Laws of Motion HELP

[covergirl]

Forces and the Laws of Motion HELP!

Homework Statement

A 4.00 kg block is pushed along the ceiling with a constant applied force of 85.0 N that acts at an angle of 55.0 degrees with the horizontal. the block accelerates to the right at 6.00 m/s2. Determine the coefficient of kinectic friction between the block and ceiling.
m=4kg
Fnet=85N
a=6m/s2

Homework Equations

uk= Fk / Fn

The Attempt at a Solution

uk= Fk / 85.0 N
sin 55 = x/85
x=69.6
uk= 69.6/85 = .82
the coefficient of kinetic friction between the block and the ceiling would be .82??


is that right??

i know this is too much to ask, but can anyone PLEASE explain to me forces and laws of motion.?? pleaseeee. i need major help about these especially with problems that have the angles and coefficient of friction..

thankss :D

 

[Kurdt]

In questions like this all you need to know is pythagorean theorem for finding the magnitudes of resulting forces and trigonometry for resolving forces.

First of all you need to resolve your force into the horizontal and vertical components using the magnitude of the force and the angle given. The normal force will of course be the vertical component. The horizontal component accelerates the block but is counteracted by the kinetic friction force. You can work out the force needed to accelerate the block at 6ms^-2 and compare it to the horizontal component of force to find the kinetic friction force.

 

[m2003]

Yes, your calculation for the coefficient of kinetic friction seems to be correct. As for an explanation of forces and the laws of motion, let's start with the basics.

Forces are any push or pull on an object. They can be exerted by one object on another, or they can be exerted by a single object on itself (such as gravity pulling a ball towards the ground). Forces can cause objects to accelerate, or change their state of motion.

The laws of motion, also known as Newton's laws of motion, are a set of three principles that describe how objects move in response to forces.

The first law, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by a net external force. This means that if there is no net force acting on an object, it will not accelerate or change its state of motion.

The second law, also known as the law of acceleration, states that the net force acting on an object is equal to the mass of the object times its acceleration. This can be written as F = ma, where F is the net force, m is the mass of the object, and a is the acceleration.

The third law, also known as the law of action and reaction, 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.

Now, let's apply these laws to your problem. In this problem, a 4.00 kg block is being pushed along the ceiling with a constant force of 85.0 N at an angle of 55.0 degrees with the horizontal. This means that there are two forces acting on the block: the applied force of 85.0 N and the force of friction between the block and the ceiling.

Using the second law, we can find the acceleration of the block by dividing the net force by the mass of the block. In this case, the net force is the applied force minus the force of friction, so we can write Fnet = ma as 85.0 N - Ff = 4.00 kg * 6.00 m/s^2.

To find the force of friction, we can use the equation Ff = uk * Fn, where uk is the coefficient