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Aloiza [94]
3 years ago
5

A 28-kg beginning roller skater is standing in front of a wall. By pushing against the wall, she is propelled backward with a ve

locity of -1.2 m/s. While pushing, her hands are in contact with the wall for 0.80 s. Ignoring frictional effects, find the magnitude and direction of the impulse acting on the skater.
Physics
1 answer:
Scorpion4ik [409]3 years ago
3 0

Answer:

33.6 Ns backward.

Explanation:

Impulse: This can be defined as the product of force and time. The S.I unit of impulse is Ns.

From Newton's second law of motion,

Impulse = change in momentum

I = mΔv................................. Equation 1

Where I = impulse, m = mass of the skater, Δv = change in velocity = final velocity - initial velocity.

Given: m = 28 kg, t = 0.8 s, Δv = -1.2-0 = -1.2 m/s (Note: the initial velocity of the skater = 0 m/s)

Substituting into equation 1

I = 28(-1.2)

I = -33.6 Ns

Thus the impulse = 33.6 Ns backward.

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What is the speaker’s power output if the sound intensity level is 102 dBdB at a distance of 25 mm ? Express your answer to two
lesya [120]

Answer:

Power  = 124.50 W

Explanation:

Given that:

The Sound intensity of a speaker output is 102 dB

and the distance r = 25 m

For the intensity of sound,

\beta (dB)= 10 \  log_{10 } (\dfrac{I}{I_o})

where;

the threshold of hearing   I_o = 10^{-12} (W/m^2)

\dfrac{102 }{10}= log_{10}( \dfrac{I}{10^{-12}})

10^{10.2} =  \dfrac{I}{10^{-12}}

I = 10^{10.2} \times 10^{-12}

I = 0.01585 W/m²

If we recall, we know remember that ;

Power = Intensity × A rea

Power = 0.01585 W/m² × 4 × 3.142 × (25 m)²

Power  = 124.50 W

7 0
3 years ago
A civil engineer must design a wheelchair-accessible ramp next to a set of steps leading up to a building. The height from the g
Westkost [7]

Answer:

A) B = 24 ft

B) H = 24.08 ft

C) M.A = 12.04

D) P = 13.7 lb

Explanation:

A)

Minimum allowable length of base of ramp can be found as follows:

Slope = H/B

where,

Slope = 1/12

H = Height of Ramp = 2 ft

B = Length of Base of Ramp = ?

Therefore,

1/12 = 2 ft/B

B = 2 ft * 12

<u>B = 24 ft</u>

B)

The length of the slope of ramp can be found by using pythagora's theorem:

L = √H² + B²

where,

H = Perpendicular = height = 2 ft

B = Base = Length of Base of Ramp = 24 ft

L = Hypotenuse = Length of Slope of Ramp = ?

Therefore,

H = √[(2 ft)² + (24 ft)²]

<u>H = 24.08 ft</u>

D)

The mechanical advantage of an inclined plane is given by the following formula:

M.A = L/H

M.A = 24.08 ft/2 ft

<u>M.A = 12.04</u>

D)

Another general formula for Mechanical Advantage is:

M.A = W/P

where,

W = Ideal Load = 165 lb

P = Ideal Effort Force = ?

Therefore,

12.04 = 165 lb/P

P = 165 lb/12.04

<u>P = 13.7 lb</u>

7 0
3 years ago
2 ways to change frictional force between 2 objects
Zanzabum
In order to change the frictional force between two solid surfaces, it can be changed by shorter distances and by the amount of weight it has or the amount of force that is pushing that object to go however distance it can. 
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3 years ago
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I hope you are able to read this question?? Help ASAP this question is on the quiz tommorow
Masteriza [31]

You would be correct.

Because you have only JUST released the arrow, and how close he is to the target, it would have the same amount of energy when it strikes the target. Yes, the kinetic energy would be destroyed when you hit the target but not right away. And yes, the potential energy would also be destroyed once you release the arrow, but it goes straight back once it stops moving, aka when it hits the target, although it has only just stopped moving.

Hope this helps!

8 0
3 years ago
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vovikov84 [41]

Answer:

All three pendulum will attain same velocity

Explanation:

All three pendulum will attain same velocity irrespective of their mass difference in isolated system (means where air drag are negligible) and at same length

As you know when velocity is calculated we can not take mass into account.  

3 0
3 years ago
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