# Movement in relative motion

#### physic1GUY

1. Homework Statement
confession Olympic hammer competition, competitor turns mass 7.3 kg ball at the end of a metal cable length 1.2 meters. Throw the hammer was released some 1.3 meters high 21 ° angle above horizon.
Last horizontal distance was 83 m hammer, what is the radial acceleration of the hammer just before liberation?

2. Homework Equations
Path equation - y=xtanTHETA - g / (2v0^2cos^2THETA) x x^2

3. The Attempt at a Solution
i set the details i know at the equation and i got a huge velocity 103.69 m/s
i put it in the equation a=v^2 / r but this is an astronom acceleration
what did i do wrong , i will glad for help and explanation...
thanks!

Related Introductory Physics Homework Help News on Phys.org

#### berkeman

Mentor
1. Homework Statement
confession Olympic hammer competition, competitor turns mass 7.3 kg ball at the end of a metal cable length 1.2 meters. Throw the hammer was released some 1.3 meters high 21 ° angle above horizon.
Last horizontal distance was 83 m hammer, what is the radial acceleration of the hammer just before liberation?

2. Homework Equations
Path equation - y=xtanTHETA - g / (2v0^2cos^2THETA) x x^2

3. The Attempt at a Solution
i set the details i know at the equation and i got a huge velocity 103.69 m/s
i put it in the equation a=v^2 / r but this is an astronom acceleration
what did i do wrong , i will glad for help and explanation...
thanks!
It would be good to see more details of your calculations. Generally in problems like this, you write one equation for the x motion as a function of time and one for the y motion as a function of time, and solve for the time where the object hits the ground. This lets you get back to the initial velocity, which will give you the centripital acceleration in the circular throwing motion just before release...

#### physic1GUY

i will post mu calculiting :
i talk the Y as the sin21 x 1.3
sin21x1.3= 83 tan21 - ( ( 9.8 x 83^2) /(2Vo^2-cos^2 21)
0.47 = 31.9- ( 67512.2)/(2Vo^2-0.88)
0.94Vo^2= 0.141+(-28072)-67512.2
-62.86Vo^2 = -28.072 - 67512.2
-62.86Vo^2 =-67540.2
V0=103/69 [m/s]
Ar=v^2/r
------------------
i didn't reference to any mass when do i need to refer it ?
thanks

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving