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N76 [4]
3 years ago
14

A high-jumper, having just cleared the bar, lands on an air mattress and comes to rest. Had she landed directly on the hard grou

nd, her stopping time would have been much shorter. Using the impulse-momentum theorem as your guide, determine which one of the following statements is correct.a. the air mattress exerts the same impulse, but a greater net average force, on the high-jumper than does the hard ground
b. the air mattress exerts a greater impulse, and a greater net average force, on the high-jumper than does the hard ground
c. the air mattress exerts a smaller impulse, and a smaller net average force, on the high-jumper than does the hard ground
d. the air mattress exerts a greater impulse, but a smaller net average force, on the high-jumper than does the hard ground
e. the air mattress exerts the same impulse, but a smaller net avg force, on the hj than hg
Physics
1 answer:
attashe74 [19]3 years ago
8 0

Answer:

Explanation:

Impulse = Force x time = change in momentum

F x t = m ( v - u )

In both cases, u are same and v=0

So change in momentum is same

hence , impulse is same.

F = Change in momentum / time

In case of air mattress , time increases

Hence average force decreases .

Option e is correct .

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A disk with a rotational inertia of 5.0 kg. m2 and a radius of 0.25 m rotates on a frictionless fixed axis perpendicu-
diamong [38]

Answer:1.6 rad/s

Explanation:

Given

moment of Inertia  of disk I=5 kg-m^2

radius of disc r=0.25 m

Force F=8 N

Torque T=I\alpha =F\cdot r

5\times \alpha =8\times 0.25

\alpha =0.4 rad/s^2

using

\theta =\omega _0\times t+\frac{\alpha t^2}{2}

\pi =0+\frac{0.4t^2}{2}

2\pi =0.4t^2

t^2=5\pi

t=\sqrt{5\pi }

t=3.96 s

\omega =\omega _0+\alpha t

\omega =0+0.4\times 3.96

\omega =1.58 rad/s\approx 1.6 rad/s

                         

3 0
4 years ago
Sarah, who has a mass of 55 kg, is riding in a car at 20 m/s. She sees a cat crossing the street and slams on the brakes! Her se
lions [1.4K]

Answer:

-2200 N

Explanation:

Here we can use the impulse theorem, which states that the impulse exerted on Sarah (product of force and duration of collision) is equal to Sarah's change in momentum:

I=\Delta p\\F \Delta t = m \Delta v

where

F is the average force

\Delta t is the duration of the collision

m is the mass

\Delta v is the change in velocity

In this problem:

m = 55 kg

\Delta v = 0-20 = -20 m/s

\Delta t = 0.5 s

Solving the formula, we find the force exerted by the seatbelt on Sarah:

F=\frac{m\Delta v}{\Delta t}=\frac{(55)(-20)}{0.5}=-2200 N

And the negative sign means the direction is opposite to that of Sarah's initial motion.

6 0
3 years ago
The velocity of an ocean wave is 5m/s. The distance between crests is 3m. What is the frequency of the wave
alexgriva [62]

Answer:

1.67m

5m/s

Explanation:

Wavelength of the wave = 3m

Speed of the wave  = 5m/s

The distance between crest and the adjacent trough of water waves is known as the wavelength of a wave.

 To find the frequency ;

        V = f∧

V is the speed of the wave

f is the frequency

∧ is the wavelength

  Insert the parameters and find the frequency;

        f  = V/ ∧   = 5 / 3  = 1.67Hz

The rate at which the wave passed a given point is the speed of the wave and it is 5m/s

4 0
3 years ago
Un ciclista recorre 10 km en 2 h.Calcula su velocidad media en km/h.¿cuantos metros recorre cada segundo
lys-0071 [83]

Answer:

La velocidad media es 5 \frac{km}{h}, que equivale a 1.389 \frac{m}{s}

Explanation:

La velocidad es una magnitud física que expresa la relación entre el espacio recorrido por un objeto y el tiempo empleado para ello.

La velocidad media relaciona el cambio de la posición con el tiempo empleado en efectuar dicho cambio. Por lo que se calcula como la distancia recorrida por un objeto dividido por el tiempo transcurrido:

velocidad=\frac{distancia}{tiempo}

En este caso:

  • distancia= 10 km= 10,000 m (siendo 1 km= 1,000 m)
  • tiempo= 2 h= 7,200 s (siendo 1 h= 3,600 s)

Entonces, reemplazando en la definición de velocidad media:

velocidad=\frac{10 km}{2 h}= \frac{10,000 m}{7,200 s}

Resolviendo se obtiene:

velocidad=5 \frac{km}{h}= 1.389\frac{m}{s}

<u><em>La velocidad media es 5 </em></u>\frac{km}{h}<u><em>, que equivale a 1.389 </em></u>\frac{m}{s}<u><em></em></u>

4 0
3 years ago
Why all planetary objects have different amount of gravity?
Paladinen [302]

Answer:

Why do scientists usually talk about mass rather than weight? An object's weight is dependent on its mass and how strongly gravity pulls on it. The strength of gravity depends on how far away one object is from another. That's why the same object weighs different amounts on different planets.

Explanation: on Google

3 0
3 years ago
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