Newton's Second Law Incline (constant accel)

In summary, the conversation discusses Newton's Second Law and its application to a block on an incline with a given mass, incline angle, and coefficient of kinetic friction. The question asks for the force required to move the block at a constant speed up the incline. Through the application of Newton's Second Law, the participants solve for the unknown applied force and discuss the direction of each force acting on the block.
  • #1
Dakren12
5
0
Newton's Second Law...Incline (constant accel)

Homework Statement



Given: mass of block of 5.0 kg
incline angle is 37theta
coeff kinetic friction is 0.50

What is the force, directed up the inline, required to move the block at constant speed up the incline?

The Attempt at a Solution



So i tried to break it up... to the y-dir and x-dir.

the forces for y-dir. I have Fn and (mg*cos37)
the forces for x-dir. I have fk and (mg*sin37)
I have answer saying its 50.. but i can't seem to figure it out!
 
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  • #2


Dakren12 said:
the forces for y-dir. I have Fn and (mg*cos37)
the forces for x-dir. I have fk and (mg*sin37)
So far, so good. What's fk equal to?

Hint: What net force must act on the block if it's to move at constant speed?
 
  • #3


so Fnet > fk?

and fk = mu k * Fn...

so... fk = (.5)(mg*cos37)?
...
so confusing.
 
  • #4


Dakren12 said:
so Fnet > fk?
No. What's does Newton's 2nd law tell you about net force and acceleration?

and fk = mu k * Fn...

so... fk = (.5)(mg*cos37)?
Good!

There are three forces acting parallel to the incline: Friction; gravity (one component of it); and the applied force up the incline (which is what you're trying to find). You can calculate the first two. And, given my hint, you can then solve for the third.
 
  • #5


sigh... i think I'm over thinking it...

so friction is approx 20
gravity is about 30...
the unknown applied force x

would i still use f=ma?

so something like (20+x)...minus 30 = 0?
...
hopeless ..
 
  • #6


Dakren12 said:
so friction is approx 20
gravity is about 30...
the unknown applied force x
Good!

would i still use f=ma?
Sure.

so something like (20+x)...minus 30 = 0?
Almost. Careful with signs. What direction does each force act? Hint: Give anything that acts up the incline a positive sign and anything that acts down the incline a negative sign. Rewrite your equation accordingly.
 
  • #7


wait a min... the fk here is acting downward huh? ... since we're pushing it upwards...

so (20 + 30) - x = 0
x = 50...!

hmm... didnt think to apply fk going downwards... haha.
 
  • #8


There you go... Not so bad after all, eh?
 
  • #9


hahah! sweet. i solved the next one as well.. which is pretty much the question in reverse! yay! thanks Doc.
 

1. What is Newton's Second Law Incline?

Newton's Second Law Incline is a concept in physics that describes the relationship between an object's mass, acceleration, and the force acting on it when it is on an inclined plane. It is an extension of Newton's Second Law, which states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration.

2. How is the acceleration of an object on an incline calculated?

The acceleration of an object on an incline can be calculated using the formula a = gsinq, where a is the acceleration, g is the acceleration due to gravity (9.8 m/s^2), and q is the angle of inclination of the plane.

3. What is the significance of Newton's Second Law Incline?

Newton's Second Law Incline is significant because it helps us understand how forces act on objects on inclined planes, which is a common scenario in real-life situations. It also allows us to calculate the acceleration and velocity of objects on inclines, which is important in fields such as engineering and physics.

4. Can Newton's Second Law Incline be applied to objects of any mass?

Yes, Newton's Second Law Incline can be applied to objects of any mass. This is because the formula for calculating acceleration takes into account the mass of the object, so the law can be applied to objects of different masses as long as the other variables such as force and angle of inclination are known.

5. How does the angle of inclination affect the acceleration of an object?

The angle of inclination has a direct effect on the acceleration of an object on an incline. The steeper the incline, the greater the acceleration will be. This is because a steeper incline means a greater component of the force of gravity is acting on the object, resulting in a larger acceleration.

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