Answer:
The coefficient of friction should in the majority of cases, remain constant no matter what your normal force is. When you apply a greater normal force, the frictional force increases, and your coefficient of friction stays the same. Here's another way to think about it: because the force of friction is equal to the normal force times the coefficient of friction, we expect (in theory) an increase in friction when the normal force is increased.
One more thing, the coefficient of friction is a property of the materials being "rubbed", and this property usually does not depend on the normal force
Only because when most people work with vertical motion, they call the upward direction positive. So falling objects have negative velocity and acceleration. But if you prefer to call the downward direction positive, you have every right to do that. Then the force of gravity on a falling object, as well as its velocity and acceleration, are all positive, and its negative altitude steadily grows until it hits the ground.
Answer:
Explanation:
The wheel and falling student will have common acceleration .
For rotational motion of wheel
Tx r = I α , T is tension in the crank , α is angular acceleration of wheel , I is moment of inertia , r is radius of the wheel.
= I a / r
T = I a / r²
For motion of student
Mg - T = Ma , M is mass of the wheel.
Mg - I a / r² = Ma
Mg = Ma +I a / r²
Mg = (M +I / r²)a
a = Mg / (M +I / r²)
= 51 x 9.8 / ( 51 + 9.6 / .3² )
499.8 / (51+ 106.67 )
= 499.8 / 157.67
= 3.17 m / s².
If time t is taken to fall by 12 m
12 = 1/2 a t²
24 / a = t²
24 / 3.17 =t²
t²= 7.57
t = 2.75 s
velocity to reach sidewalk
v = u + at
= 3.17 x 2.75
= 8.72 m / s
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth. Tide tables can be used to find the predicted times and amplitude (or "tidal range") of tides at any given locale.
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