By Newton's second law, the net vertical force acting on the object is 0, so that
<em>n</em> - <em>w</em> = 0
where <em>n</em> = magnitude of the normal force of the surface pushing up on the object, and <em>w</em> = weight of the object. Hence <em>n</em> = <em>w</em> = <em>mg</em> = 196 N, where <em>m</em> = 20 kg and <em>g</em> = 9.80 m/s².
The force of static friction exerts up to 80 N on the object, since that's the minimum required force needed to get it moving, which means the coefficient of <u>static</u> friction <em>µ</em> is such that
80 N = <em>µ</em> (196 N) → <em>µ</em> = (80 N)/(196 N) ≈ 0.408
Moving at constant speed, there is a kinetic friction force of 40 N opposing the object's motion, so that the coefficient of <u>kinetic</u> friction <em>ν</em> is
40 N = <em>ν</em> (196 N) → <em>ν</em> = (40 N)/(196 N) ≈ 0.204
And so the closest answer is C.
(Note: <em>µ</em> and <em>ν</em> are the Greek letters mu and nu)
Answer:
A.) 39.5 m
B.) 0
C.) 60m/s^2
Explanation:
Given that a displacement function of a particle is x(t)=(20t^2-15t+200).
To Find the total displacement,
Reduce everything by dividing them by 5
X(t) = 4t^2 - 3t + 40 ...... (1)
For instantaneous velocity, differentiate x(t). That is,
dy/dt = 60t - 15 ...... (2)
But dy/dt = velocity.
If dy/dt = 0, then
60t - 15 = 0
60t = 15
t = 15/60
t = 0.25s
Substitutes t in equation (1)
Total displacement will be
X(t) = 4(0.25)^2 - 3(0.25) + 40
X(t) = 0.25 - 0.75 + 40
Total displacement = 39.5 m
To calculate instantaneous velocity, substitute t into equation (2)
V = 60 (0.25) - 15
V = 0.
and to find instantaneous acceleration, differentiate dv/dt
dv/dt = 60
Therefore, acceleration = 60 m/s^2
Answer:
effeciency n = = 49%
Explanation:
given data:
mass of aircraft 3250 kg
power P = 1500 hp = 1118549.81 watt
time = 12.5 min
h = 10 km = 10,000 m
v =85 km/h = 236.11 m/s
kinetic energy
kinetic energy 
gravitational energy 
total energy 
effeciency n = = 49%
<span>553 ohms
The Capacitive reactance of a capacitor is dependent upon the frequency. The lower the frequency, the higher the reactance, the higher the frequency, the lower the reactance. The equation is
Xc = 1/(2*pi*f*C)
where
Xc = Reactance in ohms
pi = 3.1415926535.....
f = frequency in hertz.
C = capacitance in farads.
I'm assuming that the voltage and resistor mentioned in the question are for later parts that are not mentioned in this question. Reason is that they have no effect on the reactance, but would have an effect if a question about current draw is made in a later part. With that said, let's calculate the reactance.
The 120 rad/s frequency is better known as 60 Hz.
Substitute known values into the formula.
Xc = 1/(2*pi* 60 * 0.00000480)
Xc = 1/0.001809557
Xc = 552.6213302
Rounding to 3 significant figures gives 553 ohms.</span>
