The force will be 4 times smaller.
Answer:
The object would weight 63 N on the Earth surface
Explanation:
We can use the general expression for the gravitational force between two objects to solve this problem, considering that in both cases, the mass of the Earth is the same. Notice as well that we know the gravitational force (weight) of the object at 3200 km from the Earth surface, which is (3200 + 6400 = 9600 km) from the center of the Earth:
![F_G=G\,\frac{M_E\,m}{d^2} \\28\,\,N=G\,\frac{M_E\,m}{9600000^2}](https://tex.z-dn.net/?f=F_G%3DG%5C%2C%5Cfrac%7BM_E%5C%2Cm%7D%7Bd%5E2%7D%20%5C%5C28%5C%2C%5C%2CN%3DG%5C%2C%5Cfrac%7BM_E%5C%2Cm%7D%7B9600000%5E2%7D)
Now, if the body is on the surface of the Earth, its weight (w) would be:
![F_G=G\,\frac{M_E\,m}{d^2} \\w=G\,\frac{M_E\,m}{6400000^2}](https://tex.z-dn.net/?f=F_G%3DG%5C%2C%5Cfrac%7BM_E%5C%2Cm%7D%7Bd%5E2%7D%20%5C%5Cw%3DG%5C%2C%5Cfrac%7BM_E%5C%2Cm%7D%7B6400000%5E2%7D)
Now we can divide term by term the two equations above, to cancel out common factors and end up with a simple proportion:
![\frac{w}{28} =\frac{9600000^2}{6400000^2} \\\frac{w}{28} =\frac{9}{4} \\\\ \\w=\frac{9\,*\,28}{4}\,\,\,N\\w=63\,\,N \\](https://tex.z-dn.net/?f=%5Cfrac%7Bw%7D%7B28%7D%20%3D%5Cfrac%7B9600000%5E2%7D%7B6400000%5E2%7D%20%5C%5C%5Cfrac%7Bw%7D%7B28%7D%20%3D%5Cfrac%7B9%7D%7B4%7D%20%5C%5C%5C%5C%20%5C%5Cw%3D%5Cfrac%7B9%5C%2C%2A%5C%2C28%7D%7B4%7D%5C%2C%5C%2C%5C%2CN%5C%5Cw%3D63%5C%2C%5C%2CN%20%5C%5C)
Answer:
a = 2 [m/s^2]
Explanation:
To solve this problem we must use the expressions of kinematics, we must bear in mind that when a body is at rest its velocity is zero.
![v_{f} = v_{i} - (a*t)](https://tex.z-dn.net/?f=v_%7Bf%7D%20%3D%20v_%7Bi%7D%20-%20%28a%2At%29)
where:
Vf = final velocity = 0
Vi = initial velocity = 60 [m/s]
a = desacceleration [m/s^2]
t = time = 30 [s]
Note: the negative sign of the above equation means that the car is slowing down, i.e. its speed decreases.
0 = 60 - (a*30)
a = 2 [m/s^2]
Most probably physical, even though the change of liquids to solids is directly related to chemistry too