## joshi 3 years ago A wet bar of soap (m= 0.150 kg) slides down a ramp 2.0m long at an angle of 7.3 degrees. How long does it take to reach the bottom?

1. Taguja

Since it is a wet bar of soap, I assume there is no friction. If we draw the forces diagram, we found that there is a resultant force of the normal reaction N and the gravitational force F=mg and that F=mgsin(alpha). That force is equal to F=ma, therefore mgsin(alpha)=ma=>a=gsin(alpha). From the equation t=sqrt(2x/a), we get that t is approximately 1,8 seconds. Keep in mind that this is actually independent of the mass of the body.

2. joshi

ohhhh i did F=mgcos. could you explain why it's sin? also thanks

3. joshi

no the answer is infact 1.8 ...

4. Taguja

Oh yeah.. Now i forgot taking the square root LOL... 1,8 seconds is infact the right answer. I hope that this sketch helps you :P

5. joshi

ohhh i see, i calculated a y component for gravity as well which doesn't really exist in this case. well anyway, thanks! :)

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