Answer:
uk = 0.25
Explanation:
Given:-
- An object comes to stop with acceleration, a = -2.45 m/s^2
Find:-
What is the coefficient of kinetic friction between the object and the floor?
Solution:-
- Assuming the object has mass (m) that slides over a rough surface with coefficient of kinetic friction (uk). There is only Frictional force (Ff) acting in the horizontal axis on the object opposing the motion (-x direction).
- We will apply equilibrium equation on the object in vertical direction.
N - m*g = 0
N = m*g
Where, N : Contact force exerted by the surface on the floor
g : Gravitational acceleration constant = 9.81 m/s^2
- Now apply Newton's second law of motion in the horizontal ( x-direction ):
- Ff = m*a
- The frictional force is related to contact force (N) by the following expression:
Ff = uk*N
- Substitute the 1st and 3rd expressions in the 2nd equation:
uk*m*g = -m*a
uk = a / g
- Plug in the values and solve for uk:
uk = - (-2.45) / 9.81
uk = 0.25
The answer is evolution. When a specifies evolves over time they change and adapt to their environment.
Students were asked to place a mint in their mouths and determine how long it took for the mint to dissolve. The condition of the mint varied in each student group. One group of students were asked to leave a whole mint in their mouth, not moving it around, and let it dissolve. Another group swirled a mint, while the other groups used mints broken into smaller pieces. See the chart for all of the manipulated variable. After reviewing that data table, what kind of result would you predict for the swirled, whole mint?
A) The time is likely between 10-30 seconds.
B) The time is likely between 40-80 seconds.
C) The time is likely between 90-160 seconds.
D) The time is likely between 100-200 seconds.
ANSWER: B) The time is likely between 40-80 seconds.
EXPLANATION:The time is likely between 40-80 seconds.
By swirling the mint, this is agitating and creating a higher frequency of collisions between the saliva particles and mint particles, increasing the rate of dissolution. Therefore, the time is likely to be less than the mint cut in half but probably more than the mint when it is in small pieces.
A) because it is an element.
Explanation: usually when they say pure substance they mean pure element.
Hope this helped!! :)
