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Amanda [17]
3 years ago
9

A 58-kg skater is standing still in front of a wall. By pushing against the wall she propels herself backward with a velocity of

-1 m/s. Her hands are in contact with the wall for 0.80 s. Ignore friction and wind resistance. Find the magnitude and direction of the average force she exerts on the wall (which has the same magnitude, but opposite direction, as the force that the wall applies to her).
Physics
1 answer:
masha68 [24]3 years ago
5 0

Answer:

F = -72.5 N

Explanation:

You can do this excercise in two ways.

The first way is using the second law of Newton which is:

F = m*a

You should calculate the acceleration and then solve for F.

The second way is to use the formula of momentum which is:

F*t = m*V

Here, you only need to put the data of the excercise and solve for F.

Either way you do this, you'll get the same result.

I'll do it by both methods to prove it:

First method:

Assuming that the innitial speed is 0 (because is standing still) acceleration would be:

a = Vf/t

Solving for a:

a = -1/0.8 = -1.25 m/s^2

Now, let's solve for F:

F = 58 * (-1.25) = -72.5 N

Second method:

We know that F*t = m*V so:

F = m*V/t

F = 58 * (-1) / 0.8

F = -72.5 N

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You want the current amplitude through a 0.450-mH inductor (part of the circuitry for a radio receiver) to be 1.90 mA when a sin
faust18 [17]

Answer:

Frequency required will be 2421.127 kHz

Explanation:

We have given inductance L=0.450H=0.45\times 10^{-3}H

Current in the inductor i=1.90mA=1.90\times 10^{-3}A

Voltage v = 13 volt

Inductive reactance of the circuit X_l=\frac{v}{i}

X_l=\frac{13}{1.9\times 10^{-3}}=6842.10ohm

We know that

X_l=\omega L=2\pi fL

2\times 3.14\times  f\times 0.45\times 10^{-3}=6842.10

f = 2421.127 kHz

6 0
3 years ago
A projectile is fired from the origin (at y = 0 m) as shown in the diagram. The initial velocity
Viktor [21]

Answer:

-26 m/s.

Explanation:

Hello,

In this case, since the vertical initial velocity is 26 m/s and the vertical final velocity is 0 m/s at P, we compute the time to reach P:

t=\frac{0m/s-26m/s}{-9.8m/s^2} =2.65s

With which we compute the maximum height:

y=26m/s*2.65s-\frac{1}{2}*9.8m/s^2*(2.65s)^2 \\\\y=34.5m

Therefore, the final velocity until the floor, assuming P as the starting point (Voy=0m/s), turns out:

v_f=\sqrt{0m/s-(-9.8m/s^2)*2*34.5m}\\ \\v_f=-26m/s

Which is clearly negative since it the projectile is moving downwards the starting point.

Regards.

3 0
3 years ago
Please help help me please
vodomira [7]
The answer is either c or d but c is the best answer
4 0
3 years ago
If a car goes around a corner at a constant 20 miles/hour, does its velocity change?
UNO [17]

Answer:

yes

Explanation:

velocity changes either in magnitude (an increase or decrease in speed) or in direction, or both

3 0
3 years ago
Read 2 more answers
A relaxed spring of length 0. 13 m stands vertically on the floor; its stiffness is 1180 N/m. You release a block of mass 0. 5 k
Daniel [21]

The length of spring when the block comes momentarily to rest on the compressed spring will be 0.054 m.The length of the spring by the letter x.

<h3>What is the potential energy of the spring?</h3>

The energy is stored in the spring when it is stretched or compressed by some length. It is the product of mass, gravity and distance compressed or stretched. Mathrmatically it is given by;

PE=mgh

The given data in the problem is ;

m is the mass of the block is 0.5 kg height,

h is the height is released is 0.7 m

x initial length of the spring = 0.13 m.

K is the force constant of the spring = 1180 N/m.

By the law of conservation of energy,

The potential energy of the spring gets converted

\rm mgh=\frac{1}{2}KL^2 \\\\ \rm L= \sqrt{\frac{2mgh}{K} } \\\\ \rm L= \sqrt{\frac{2\times 0.5\times9.81 \times 0.7}{1180} \\\\  \\\\

\rm L= 0.054m

Hence the length of spring when the block comes momentarily to rest on the compressed spring will be 0.054 m

To learn more about the potential energy of the spring refer to the link;

brainly.com/question/2730954

4 0
2 years ago
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