Answer:
Explanation:A driver slowing down to stop at a light is accelerating. ... acceleration is opposite to the motion, the speed of the object decreases. The car slows down. Slowing down is also called negative acceleration.
elastic is the correct answer
I think it is the red giant
Answer:
a)
, b) ![R = 0.312\,m](https://tex.z-dn.net/?f=R%20%3D%200.312%5C%2Cm)
Explanation:
a) The minimum coeffcient of friction is computed by the following expression derived from the Principle of Energy Conservation:
![\frac{1}{2}\cdot k \cdot x^{2} = \mu_{k}\cdot m\cdot g \cdot \Delta s](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20k%20%5Ccdot%20x%5E%7B2%7D%20%3D%20%5Cmu_%7Bk%7D%5Ccdot%20m%5Ccdot%20g%20%5Ccdot%20%5CDelta%20s)
![\mu_{k} = \frac{k\cdot x^{2}}{2\cdot m\cdot g \cdot \Delta s}](https://tex.z-dn.net/?f=%5Cmu_%7Bk%7D%20%3D%20%5Cfrac%7Bk%5Ccdot%20x%5E%7B2%7D%7D%7B2%5Ccdot%20m%5Ccdot%20g%20%5Ccdot%20%5CDelta%20s%7D)
![\mu_{k} = \frac{\left(8050\,\frac{N}{m} \right)\cdot (0.06\,m)^{2}}{2\cdot (0.3\,kg)\cdot (9.807\,\frac{m}{s^{2}} )\cdot (7\,m)}](https://tex.z-dn.net/?f=%5Cmu_%7Bk%7D%20%3D%20%5Cfrac%7B%5Cleft%288050%5C%2C%5Cfrac%7BN%7D%7Bm%7D%20%5Cright%29%5Ccdot%20%280.06%5C%2Cm%29%5E%7B2%7D%7D%7B2%5Ccdot%20%280.3%5C%2Ckg%29%5Ccdot%20%289.807%5C%2C%5Cfrac%7Bm%7D%7Bs%5E%7B2%7D%7D%20%29%5Ccdot%20%287%5C%2Cm%29%7D)
![\mu_{k} = 0.704](https://tex.z-dn.net/?f=%5Cmu_%7Bk%7D%20%3D%200.704)
b) The speed of the block is determined by using the Principle of Energy Conservation:
![\frac{1}{2}\cdot k \cdot x^{2} = \frac{1}{2}\cdot m \cdot v^{2}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20k%20%5Ccdot%20x%5E%7B2%7D%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20m%20%5Ccdot%20v%5E%7B2%7D)
![v = x\cdot \sqrt{\frac{k}{m} }](https://tex.z-dn.net/?f=v%20%3D%20x%5Ccdot%20%5Csqrt%7B%5Cfrac%7Bk%7D%7Bm%7D%20%7D)
![v = (0.06\,m)\cdot \sqrt{\frac{8050\,\frac{N}{m} }{0.3\,kg} }](https://tex.z-dn.net/?f=v%20%3D%20%280.06%5C%2Cm%29%5Ccdot%20%5Csqrt%7B%5Cfrac%7B8050%5C%2C%5Cfrac%7BN%7D%7Bm%7D%20%7D%7B0.3%5C%2Ckg%7D%20%7D)
![v \approx 9.829\,\frac{m}{s}](https://tex.z-dn.net/?f=v%20%5Capprox%209.829%5C%2C%5Cfrac%7Bm%7D%7Bs%7D)
The radius of the circular loop is:
![\Sigma F_{r} = -90\,N -(0.3\,kg)\cdot (9.807\,\frac{m}{s^{2}} ) = -(0.3\,kg)\cdot \frac{v^{2}}{R}](https://tex.z-dn.net/?f=%5CSigma%20F_%7Br%7D%20%3D%20-90%5C%2CN%20-%280.3%5C%2Ckg%29%5Ccdot%20%289.807%5C%2C%5Cfrac%7Bm%7D%7Bs%5E%7B2%7D%7D%20%29%20%3D%20-%280.3%5C%2Ckg%29%5Ccdot%20%5Cfrac%7Bv%5E%7B2%7D%7D%7BR%7D)
![\frac{\left(9.829\,\frac{m}{s}\right)^{2}}{R} = 309.807\,\frac{m}{s^{2}}](https://tex.z-dn.net/?f=%5Cfrac%7B%5Cleft%289.829%5C%2C%5Cfrac%7Bm%7D%7Bs%7D%5Cright%29%5E%7B2%7D%7D%7BR%7D%20%3D%20309.807%5C%2C%5Cfrac%7Bm%7D%7Bs%5E%7B2%7D%7D)
![R = 0.312\,m](https://tex.z-dn.net/?f=R%20%3D%200.312%5C%2Cm)