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a_sh-v [17]
4 years ago
7

A spring balance consists of a pan that hangs from a spring. A damping force Fd = −bv is applied to the balance so that when an

object is placed in the pan it comes to rest in the minimum time without overshoot. Determine the required value of b for an object of mass 2.5 kg that extends the spring by 6.0 cm. (Assume g = 9.81 m s−2.) 2.
Physics
1 answer:
Citrus2011 [14]4 years ago
5 0

Answer:

b ≈ 64 Kg/s

Explanation:

Given

Fd = −bv

m = 2.5 kg

y = 6.0 cm = 0.06 m

g = 9.81 m/s²

The object in the pan comes to rest in the minimum time without overshoot. this means that damping is critical (b² = 4*k*m).

m is given and we find k from the equilibrium extension of 6.0 cm (0.06 m):

∑Fy = 0 (↑)

k*y - W = 0    ⇒   k*y - m*g = 0   ⇒   k = m*g / y

⇒   k = (2.5 kg)*(9.81 m/s²) / (0.06 m)

⇒   k = 408.75 N/m

Hence, if

b² = 4*k*m    ⇒     b = √(4*k*m) = 2*√(k*m)

⇒     b = 2*√(k*m) = 2*√(408.75 N/m*2.5 kg)

⇒     b = 63.9335 Kg/s ≈ 64 Kg/s

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A neutron at rest decays (breaks up) to a proton and an electron. Energy is released in the decay and appears as kinetic energy
SashulF [63]

Answer:

5.444\times 10^{-4}

Explanation:

The momentum of the neutron before and after the decay  is the same since there's no external force.

P_{sys}=const\\\\P=mv\\\\K=0.5mv^2

#The neutron is initially at rest, so after the decay:

P_A+P_B=0\\\\P_A=-P_B

#After decay, the proton has +ve direction  with a velocity v_Awhile the electron moves in a negative direction with a velocity v_B

Therefore:

P_A=m_Av_A, P_B=m_Bv_B\\\\\therefore m_Av_A,=m_Bv_B

Let the energy released during the decay be Q:

Q=K_{tot}=K_A+K_B\\\\Q=K_A+0.5m_Bv_B^2\\\\Q=K_A+0.5m_B(\frac{m_A}{m_B})^2v_A^2\\\\\ But \ K_A=0.5m_Av_A^2\\\\\therefore Q=K_A+\frac{m_A}{m_B}K_A=K_A(1+\frac{m_A}{m_B})\\\\=Q=\frac{m_A+m_B}{m_B}K_A\\\\m_A=1836m_B\\\\\frac{K_A}{Q}=\frac{m_B}{1836m_B+m_B}=\frac{1}{1837}\\\\\frac{K_A}{Q}=5.444\times10^{-4}

Hence,Kp/Ktot is 5.444x10^(-4)

4 1
3 years ago
In trial 1 of an experiment, a cart moves with a speed of vo on a frictionless, horizontal track and collides with another cart
marta [7]

Answer:

1) elastic shock, the velocity of the center of mass does not change

2) inelastic shock, he velocity of the mass center   change

Explanation:

The position of the center of mass of your system is defined by

          x_{cm} = \frac{1}{M} \sum x_i m_i

in this case we have two bodies

          x_{cm} = \frac{1}{M} (x₁m₁ + x₂ m₂)

the velocity of the center of mass is

          x_{cm} = dx_{cm} / dt = \frac{1}{M} ( m_1 \frac{dx_1}{dt} \ + m_2 \frac{dx_2}{dt} )

          x_{cm} = \frac{1}{M} ( m_1 v_1 + m_2 v_2 )

where M is the total mass of the system.

Therefore to answer this question we have to find the velocity of the body after the collision.

Let's use momentum conservation, where the system is formed by the two bodies, so that the forces have been internal during the collision.

Let's solve each case separately.

2) inelastic shock

initial instant. Before the crash

         p₀ = m₁ v₀ + 0

final instant. After the collision with the cars together

        p_f = (m₁ + m₂) v

         p₀ = p_f

         m₁ v₀ = (m₁ + m₂) v

         v = \frac{m_1}{m_1+m_2}  v₀

let's find the velocity of the center of mass

         M = m₁ + m₂

initial.

         v_{cm o} = \frac{1}{m_1 +m_2} (m₁ vo)

final

         v_{cm f} = \frac{1}{M} ( \frac{m_1}{m_1 + m_2} v_o ) ( v) = v

         v_{cm f} =  \frac{m_1}{M^2} v_o

Let's find the ratio of the velocities of the center of mass

          vcmf / vcmo = \frac{1}{M} = \frac{1}{m_1 +m_2}

           

           

therefore the velocity of the mass center   change

1) elastic shock

initial instant.

           p₀ = m₁ v₀

final moment

           p_f = m₁ v_{1f} + m₂ v_{2f}

           p₀ = p_f

           m₁ v₀ = m₁ v_{1f} + m₂ v_{2f}

           m₁ (v₀ - v_{2f}) = m₂ v_{2f}

in this case the kinetic energy is conserved

           K₀ = K_f

          ½ m₁ v₀² = ½ m₁ v_{1f}² + ½ m₂ v_{2f}²

           m₁ (v₀² - v_{1f}²) = m₂ v_{2f}²

           m₁ (v₀ + v_{1f}) (v₀ - v_{1f}) = m₂ v_{2f}

we write our system of equations

           m₁ (v₀ - v_{1f}) = m₂ v_{2f}             (1)

           m₁ (v₀ - v_{1f}) (v₀ + v_{1f}) = m₂ v_{2f}²

we solve the system

             v₀ + v_{1f} = v_{2f}

we substitute and look for the final speeds

             v_{1f} = \frac{m_1 -m_2}{m1 +m2 } v_o

             v_{2f} = \frac{2 m_1}{m-1+m_2} vo

now let's find the velocity of the center of mass

initial

          v_{cm o} = \frac{1}{M} m₁ v₀

final

          v_{cm f} = \frac{1}{M}  (m₁ v_{1f} + m₂ v_{2f} )

          v_{cm f} = \frac{1}{M} [  m_1  \frac{m_2}{M} + m_2  \frac{2 m_1}{M} ] v₀

          v_{cm f} = \frac{1}{M^2} ( m₁² - m₁m₂ +2 m₁m₂) v₂

          v_{cm f} = \frac{1}{M^2} (m₁² + m₁ m₂) v₀

let's look for the relationship

         v_{cm f} / v_{cm o} = \frac{1}{M} M

         v_{cm f} / v_{cm o} = 1

therefore the velocity of the center of mass does not change

we see in either case the velocity of the center of mass does not change.

4 0
3 years ago
You throw a baseball with a mass of 0.5 kg. The ball leaves your hand with a speed of 35 m/s. Calculate the kinetic energy. (SHO
mixas84 [53]

Answer:

The kinetic energy of the baseball is 306.25 joules.

Explanation:

SInce the baseball can be considered a particle, that is, that effects from geometry can be neglected, the kinetic energy (K), in joules, is entirely translational, whose formula is:

K = \frac{1}{2}\cdot m\cdot v^{2} (1)

Where:

m - Mass, in kilograms.

v - Speed, in meters per second.

If we know that m = 0.5\,kg and v = 35\,\frac{m}{s}, then the kinetic energy of the baseball thrown by the player is:

K = \frac{1}{2}\cdot m \cdot v^{2}

K = 306.25\,J

The kinetic energy of the baseball is 306.25 joules.

6 0
3 years ago
A person on a sled coasts down a hill and then goes over a slight rise with speed 2.7 m/s. The top of the rise can be modeled as
Paladinen [302]
Since we're dealing with radial acceleration around a circle, I used the radial acceleration equation a=v²/r. At the top of the hill, the force upward exerted by the hill is less than the weight of the sled.  if v is large enough the term (g-v²/r) will become 0 and the sled will fly off the ground as it reaches the peak.  Let me know if I can clarify any of my work.

8 0
3 years ago
A mass of 10.0 kg is in a gravitational field of 3.50 N/kg. What force acts on the mass?
mash [69]

Answer:

Force=35 N

Explanation:

Given data

mass m=10.0 kg

Gravitational field E=3.50 N/kg

To find

Force

Solution

From definition of gravitational field intensity.

E_{gravitational-field }=\frac{Force}{mass}\\  E=F/m\\F=mE\\F=(10.0 kg)*(3.50 N/kg)\\F=35N

6 0
4 years ago
Read 2 more answers
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