Ask question

Ask question

All categories

julia-pushkina [17]

2 years ago

9

While a roofer is working on a roof that slants at 36° above the horizontal, he accidentally nudges his 85.0-N toolbox, causing

it to start sliding downward from rest. If it starts 4.25 m from the lower edge of the roof, how fast will the toolbox be mov- ing just as it reaches the edge of the roof if the kinetic friction force on it is 22.0 N?

1 answer:

Troyanec [42]2 years ago

7 0

Answer:

$v = 5.23 m/s$

Explanation:

As the tool box start slipping from the roof we can say that work done by all forces on it will be equal to change in its kinetic energy

so we have

$W_f + W_g = \frac{1}{2}mv^2 - 0$

here we know that

$W_f = - F_f .d$

so we will have

$W_f = - 22(4.25) = -93.5 J$

now work done by gravity is given as

$W_g = mgsin\theta(d)$

$W_g = 85 sin36(4.25)$

$W_g = 212.33 J$

now we have

$212.33 - 93.5 = \frac{1}{2}(\frac{85}{9.8})v^2$

$v = 5.23 m/s$

You might be interested in

A mass is tied to a string and swung in a horizontal circle with a constant angular speed. show answer No Attempt If this speed

Liono4ka [1.6K]

Answer:

The tension in the string is quadrupled i.e. increased by a factor of 4.

Explanation:

The tension in the string is the centripetal force. This force is given by

$F = \dfrac{mv^2}{r}$

m is the mass, v is the velocity and r is the radius.

It follows that $F \propto v^2$ , provided m and r are constant.

When v is doubled, the new force, $F_1$ , is

$F_1 = \dfrac{m(2v)^2}{r} = \dfrac{4mv^2}{r} = 4\dfrac{mv^2}{r} = 4F$

Hence, the tension in the string is quadrupled.

8 0

2 years ago

Biologists have studied the running ability of the northern quoll, a marsupial indigenous to Australia. In one set of experiment

Dominik [7]

Answer:

$\mu=0.74$

Explanation:

It is given that,

Speed of one quoll around a curve, v = 3.2 m/s (maximum speed)

Radius of the curve, r = 1.4 m

On the curve, the centripetal force is balanced by the frictional force such that the coefficient of frictional is given by :

$\mu=\dfrac{v^2}{rg}$

$\mu=\dfrac{(3.2\ m/s)^2}{1.4\ m\times 9.8\ m/s^2}$

$\mu=0.74$

So, the coefficient of static friction between the quoll's feet and the ground in this trial is 0.74. Hence, this is the required solution.

6 0

2 years ago

Read 2 more answers

Which muscle disorder does donna’s doctor diagnose? donna is suffering from leg pain in which the calf muscles contract involunt

Kay [80]

Donna's doctor must have diagnosed her with muscle cramps. With the given symptoms above, it is likely that she is experiencing muscle cramps. Muscle cramps most likely happen when the individual experiencing it is lack of fluid intake, causing the muscles to tighten causing pain and for the muscle to contract involuntarily.

7 0

2 years ago

Read 2 more answers

If a current of 2.4 a is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

Gnom [1K]

The average current density in the wire is given by:

$J=\frac{I}{A}$

where I is the current intensity and A is the cross-sectional area of the wire.

The cross-sectional area of the wire is given by:

$A=\pi r^2$

where r is the radius of the wire. In this problem, $r=\frac{d}{2}=\frac{2.0 mm}{2}=1.0 mm=0.001 m$ , so the cross-sectional area is

$A=\pi (0.001 m)^2=3.14 \cdot 10^{-6} m^2$

and the average current density is

$J=\frac{I}{A}=\frac{2.4 A}{3.14 \cdot 10^{-6} m^2}=7.64 \cdot 10^5 A/m^2$

8 0

2 years ago

Read 2 more answers

Two speakers, A and B, produce identical sound waves. A listener is 3.2 m away from speaker A. The listener finds the lowest fre

earnstyle [38]

Answer:

0.83 m or 5.57 m

Explanation:

Destructive interference will occur when the distances from the speakers differ by 1/2 wavelength.

The length of 1 cycle of 72.4 Hz is ...

λ = v/f = (343 m/s)/(72.4 Hz) ≈ 4.738 m

So, the distance of the listener from speaker B is ...

3.2 m ± (4.738 m)/2 = {0.83 m, 5.57 m} . . . either of these distances

_____

The location could be at additional multiples of 4.738 m, but we think not. The sound intensity drops off with the square of the distance from the speaker, so identical sound waves from the speakers will sound quite different at different distances from the speakers. For best interference, the distances need to be as close to the same as possible. That will be at 3.2 m and 5.57 m.

_____

<em>Comment on the speed of sound</em>

We don't know what speed you are to use for the speed of sound. We have used 343 m/s. Some sources use 340 m/s, which will give a result different by 2 or 3 cm.

8 0

2 years ago