Velocity of a box going up an inclined plane.

AI Thread Summary
A box is launched up a frictionless incline at a 20-degree angle with an initial velocity of 10 m/s. The calculation involves using the equation v = u + at, where gravity's effect needs to be factored in. The initial solution incorrectly used values for acceleration, leading to confusion about the final velocity after 3 seconds. Upon review, the correct acceleration value should have been consistently applied, resolving the discrepancy. The final answer was confirmed to be accurate after correcting the numerical error.
Berean7
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Homework Statement



A box is hurled up an incline plane of 20 degrees at 10m/second. There is no friction. What is the velocity after 3 seconds. I know gravity and the sin of 20 degrees has to be factored in.

Homework Equations



v=u+at. u is initial velocity, v is velocity after 3 seconds, t is time.

The Attempt at a Solution

9.81x.342=3.355ms^-2. Using the above equation I calculate -.065m/s (10-3.55x3). This does not match any of my answers. I do not know were I went off-track.
 
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Welcome to Physics Forums, Berean7.

I agree with your acceleration. I see that (10-3.55x3) is u+at, but were did that
-0.65 m/s come from?
 
Berean7 said:

Homework Statement



A box is hurled up an incline plane of 20 degrees at 10m/second. There is no friction. What is the velocity after 3 seconds. I know gravity and the sin of 20 degrees has to be factored in.

Homework Equations



v=u+at. u is initial velocity, v is velocity after 3 seconds, t is time.

The Attempt at a Solution

9.81x.342=3.355ms^-2. Using the above equation I calculate -.065m/s (10-3.55x3). This does not match any of my answers. I do not know were I went off-track.

Check out the two numbers 3.355 and 3.55 in your analysis.

Chet
 
Good catch, Chet.

I should know better than to answer questions after hours of grading final exams...
 
Thank you 4 the replies. .355 should have been used in both spots. I just typed it wrong. I arrived at the right answer.
 
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