Force of Object on Inclined Place

[paigegail]

I need extra help. I'm studying for my Final Exam which is tomorrow and I cannot remember how to find forces of objects on an inclined plane. The question I'm having troubles with is:
A 12.5 kg crate is placed on a ramp that is at an angle of 22 degrees from the horizontal. Find the acceleration of the crate would be down the ramp:
a) in the absence of friction (answer 3.67 m/s-squared down slope)
b) if the coefficient of kinetic friction is 0.0 (0.95 m/s-squared down slope)
I have tried this and I know that I need to find the force of Gravity that is parallel to the direction the box is going. But I keep getting like 347 and then an answer of like 20.0 something m/s-squared. What am I doing wrong?

 

[MikeH]

You should be doing this:
122.5sin22 = 45.9N or 45.9kg m/s^2

Fnet = ma
a = Fnet/m
a = (45.9kg m/s^2)/(12.5kg)
a = 3.67 m/s^2

 

[M98Ranger]

Finding the forces on an inclined plane can be a tricky concept, especially when there are different scenarios involved such as the presence or absence of friction. Here are some steps that may help you in solving this problem:

1. Draw a free body diagram: This will help you visualize all the forces acting on the crate. Draw a horizontal line to represent the surface of the inclined plane and then draw a line representing the crate, with its weight acting downwards and the normal force acting perpendicular to the surface.

2. Break down the weight force: The weight of the crate can be broken down into two components - one parallel to the surface of the incline and one perpendicular to it. The component parallel to the surface is the force that will cause the crate to accelerate down the ramp.

3. Apply Newton's Second Law: The net force acting on the crate will be equal to its mass multiplied by its acceleration. In this case, the net force will be the component of the weight force parallel to the surface of the incline.

4. Calculate the acceleration: Use the formula F=ma to calculate the acceleration of the crate. Remember to use the component of the weight force parallel to the surface of the incline as the force.

5. Consider the presence of friction: If friction is present, you will need to subtract the force of friction from the net force. The force of friction can be calculated by multiplying the coefficient of friction by the normal force.

6. Solve for the acceleration: Once you have all the necessary components, plug them into the formula from step 4 and solve for the acceleration.

In the given problem, it seems like you may have forgotten to break down the weight force into its components or you may have used the full weight force instead of the component parallel to the surface. Make sure to double check your calculations and use the correct values for the forces involved.

I hope this helps and good luck on your final exam!