Calculating Initial Acceleration for a Steel Object on a Rail | 21 N Tension

In summary, the problem involves finding the initial acceleration of a steel object being pulled along a steel rail by a cord with a tension of 21 N at a 45 degree angle. The coefficients of static, kinetic, and rolling resistance are given. Using the equations F=ma and Fp=21 N, the net forces were separated into x and y directions and solved for the acceleration, taking into account the kinetic friction coefficient and normal force. It is important to check that static friction is overcome first and to use significant figures in calculations involving measurements.
  • #1
rysezhae
3
0

Homework Statement



I need to find the initial acceleration of a steel object that weighs .89 kg, that is pulled along a steel a rail by a cord. The cord is at an 45 degree angle and has a tension of 21 N. The friction coefficents(spelled right?) of steel on steel are: .8 for static friction, .6 for kinetic friction and .002 for for rolling friction.

Homework Equations


F=ma
Fp=21 N


The Attempt at a Solution


What i did was separate the net forces into the x direction and the y direction. In the x direction i got Fpcos(theta)-Fk=max (x = x direction). I then solved for ax giving me (Fpcos(theta)-Fk)/m.
Since Fk =ukFn (kinetic friction coefficent * normal force), i substituted that in for Fk in ax. In the y direction i got, Fpsin(theta)+Fn-Fe=0. I solved for Fn then substituted that back in for Fn in the ax equation getting: (Fpcos(theta)-uk(Fe-Fpsin(theta)))/m. No sig figs required, since the problem doesn't say anything about it
 
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  • #2
##\cos(45^\circ)=\sin(45^\circ)=1/\sqrt{2}##

I'd have wanted to see you check that static friction is overcome first.

You require sig figs whenever you have measurements in your calculations - or do you think the values given are infinitely accurate?

Did you have a question?
 
  • #3
rysezhae said:
.002 for rolling friction.
What's rolling here? If the object can roll then you might need to worry about moment of inertia. (I dislike the term 'rolling friction'. Sometimes people confuse it with static friction. It is often not a form of friction, but rather of imperfect elasticity. 'Rolling resistance' is better.)
 

What is initial acceleration?

Initial acceleration is the rate at which an object's velocity changes during the first moments of its motion.

How is initial acceleration calculated?

Initial acceleration can be calculated by dividing the change in velocity by the time it takes to reach that velocity. This can be represented by the equation a = (vf - vi)/t, where a is acceleration, vf is final velocity, vi is initial velocity, and t is time.

What factors affect initial acceleration?

The factors that affect initial acceleration include the mass of the object, the force acting upon it, and any external factors such as friction or air resistance.

How does initial acceleration differ from constant acceleration?

Initial acceleration only refers to the acceleration at the beginning of an object's motion, while constant acceleration refers to a situation where the acceleration remains the same throughout the entire motion.

Why is initial acceleration important?

Initial acceleration is important because it helps us understand the motion of an object and its change in velocity. It also allows us to predict and calculate the object's future motion and behavior.

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