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3 years ago

A. What is the coefficient of kinetic friction?

Physics

1 answer:

Andrews [41]3 years ago

7 0

Explanation:

Coefficient of kinetic friction is the resistive force that opposes the motion of a body as it moves and is in contact with another body.

It is found by dividing the frictional force by the normal force.

Friction is a force that opposes motion.
Static friction is for bodies that are not in motion
Kinetic friction is for moving bodies.

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A helicopter is traveling with a velocity of 12 m/s directly upward.

Irina-Kira [14]

Answer:

H = 27.35 m

Explanation:

From projectile motion, we know that;

h = (v_o)²/2g

Where;

v_o = 12 m/s

g = 9.8 m/s²

Thus;

h = 12²/(2 × 9.8)

h = 144/19.6

h = 7.35 m

Now, we are told that when the man is 20 m above the pillow, he lets go of

the rope.

Thus, greatest height reached by the man above the ground is;

H = 20 + h

H = = 20 + 7.35

H = 27.35 m

5 0

3 years ago

Even when the head is held erect, as in the figure below, its center of mass is not directly over the principal point of support

alexandr1967 [171]

We are asked to determine the force required by the neck muscle in order to keep the head in equilibrium. To do that we will add the torques produced by the muscle force and the weight of the head. We will use torque in the clockwise direction to be negative, therefore, we have:

$\Sigma T=r_{M\perp}(F_M)-r_{W\perp}(W)$

Since we want to determine the forces when the system is at equilibrium this means that the total sum of torque is zero:

$r_{M\perp}(F_M)-r_{W\perp}(W)=0$

Now, we solve for the force of the muscle. First, we add the torque of the weight to both sides:

$r_{M\perp}(F_M)=r_{W\perp}(W)$

Now, we divide by the distance of the muscle:

$(F_M)=\frac{r_{W\perp}(W)}{r_{M\perp}}$

Now, we substitute the values:

$F_M=\frac{(2.4cm)(50N)}{5.1cm}$

Now, we solve the operations:

$F_M=23.53N$

Therefore, the force exerted by the muscles is 23.53 Newtons.

Part B. To determine the force on the pivot we will add the forces we add the vertical forces:

$\Sigma F_v=F_j-F_M-W$

Since there is no vertical movement the sum of vertical forces is zero:

$F_j-F_M-W=0$

Now, we add the force of the muscle and the weight to both sides to solve for the force on the pivot:

$F_j=F_M+W$

Now, we plug in the values:

$F_j=23.53N+50N$

Solving the operations:

$F_j=73.53N$

Therefore, the force is 73.53 Newtons.

8 0

1 year ago

I need an answer for this plzz!!<br>number 2 <br>anybody can help ??

Anuta_ua [19.1K]

2.1) (i) W = mg downwards
(ii) N = R = Normal Reaction from the ground upwards
(iii) Fe = Force of engine towards the right
(iv) f = friction towards the left
(v) ma = Constant acceleration towards right.
2.2.1)
v = 25 m/s
u = 0 m/s
∆v = v - u = (25 - 0) m/s = 25 m/s
x = X
∆t = 50 s
$a \: = \: \frac{dv}{dt} \: = \: \frac{25 \: \frac{m}{s} }{50 \: s} \: = \: 0.5 \: \frac{m}{ {s}^{2} }$
a = 0.5 m/s².
2.2.2)
F = ma = 900 kg × 0.5 m/s² = 450 N.
2.2.3)
$2ax \: = \: {v}^{2} \: - \: {u}^{2}$
$x \: = \: \frac{ {v}^{2} \: - \: {u}^{2} }{2a} \: = \: \frac{{(25 \: \frac{m}{s})}^{2} \: - \: {(0 \: \frac{m}{s} )}^{2} }{2 \: \times \: 0.5 \: \frac{m}{ {s}^{2} } } \: = \: 625 \: m$
2.3)
Fe = f + ma
Fe - f = ma
For velocity to be constant,
a should be 0, or, a = 0,
Fe = f = 270 N
2.4.1)
v = 0
u = 25 m/s
a = -0.5 m/s²
v = u + at
t = -u/a = -(25)/(-0.5) = 50 s.
2.4.2)
x = -625/(2×(-0.5)) = 625 m.

8 0

3 years ago

G a magnetic field perpendicular to the plane of a wire loop is uniform in space but changes with time t in the region of the lo

Luden [163]

Answer:

e = Δφ / Δt induced emf is proportional to enclosed flux

Also φ = B * A flux is proportional to area and enclosed field

If the induced emf e increases with time than the flux and hence the magnetic field is increasing with time (replace B with G)

Since e = ΔG * A / Δt if e is linear then G must also be linear and be proportional to the time

6 0

2 years ago

All of the following elements produce magnetic fields except

KatRina [158]

The answer should be copper. hope this helps :D

6 0

3 years ago

Read 2 more answers