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LUCKY_DIMON [66]

2 years ago

8

A 762 kg car experiences a braking force of 9045 N and skids to a stop in 4.3 seconds. What is the speed of the car just before

the braking force was applied?

1 answer:

PilotLPTM [1.2K]2 years ago

6 0

Answer:

The solution for this problem is:

We will be using the formula for force which is F = ma

=>10,000 = 2000 * a

but we need to solve for acceleration so divide both sides by 2000, we will get:

=>a = 5 m/s^2

Let the initial velocity was u m/s

=>By v = u - at

=>0 = u - 5 x 6

Since acceleration is constant the velocity can be computed by multiplying the acceleration by 6 seconds.

=>u = 30 m/s

Explanation:

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A commuter train passes a passenger platform at a constant speed of 40.4 m/s. The train horn is sounded at its characteristic fr

mihalych1998 [28]

(a) -83.6 Hz

Due to the Doppler effect, the frequency of the sound of the train horn appears shifted to the observer at rest, according to the formula:

$f' = (\frac{v}{v\pm v_s})f$

where

f' is the apparent frequency

v = 343 m/s is the speed of sound

$v_s$ is the velocity of the source of the sound (positive if the source is moving away from the observer, negative if it is moving towards the observer)

f is the original frequency of the sound

Here we have

f = 350 Hz

When the train is approaching, we have

$v_s = -40.4 m/s$

So the frequency heard by the observer on the platform is

$f' = (\frac{343 m/s}{343 m/s - 40.4 m/s})(350 Hz)=396.7 Hz$

When the train has passed the platform, we have

$v_s = +40.4 m/s$

So the frequency heard by the observer on the platform is

$f' = (\frac{343 m/s}{343 m/s + 40.4 m/s})(350 Hz)=313.1 Hz$

Therefore the overall shift in frequency is

$\Delta f = 313.1 Hz - 396.7 Hz = -83.6 Hz$

And the negative sign means the frequency has decreased.

(b) 0.865 m

The wavelength and the frequency of a wave are related by the equation

$v=\lambda f$

where

v is the speed of the wave

$\lambda$ is the wavelength

f is the frequency

When the train is approaching the platform, we have

v = 343 m/s (speed of sound)

f = f' = 396.7 Hz (apparent frequency)

Therefore the wavelength detected by a person on the platform is

$\lambda' = \frac{v}{f'}=\frac{343 m/s}{396.7 Hz}=0.865m$

5 0

3 years ago

A 7-kg bowling ball moving at 4 m/s strikes a 1 kg bowling pin. If the ball slows to 2 m/s in 0.05 s, how much force does it exe

iren [92.7K]

Answer:

280 N

Explanation:

acceleration = v2-v1 / time taken = (2-4 )/ 0.05 = -40 m/s^2 ( neg sign indicates slowing down )

force exerted = ma = 7 kg x -40 m/s^2 = - 280 N ( neg sign means opposite direction of initial velocity )

since the 7 kg ball is slowing down, the direction of force will be opposite of the initial velocity , and it will be 280 N

7 0

3 years ago

What is the unit for weight?

Ludmilka [50]

Answer:

Unit of weight is Newton(N)

Explanation:

3 0

3 years ago

Read 2 more answers

A boy drops a 0.10 kg stone down a 150 m well and listens for the echo. The air temperature is 20°C. How long after the stone is

S_A_V [24]

Use formula for Echo which is Velocity=2(Distance)/time so 343=2(150)/T 343T=300..T=300/343=0.9 seconds

4 0

3 years ago

Approximate the human form as an unclothed vertical cylinder of 0.3 m diameter and 1.75 m length with a surface temperature of 3

Zolol [24]

Answer:

$q=1118.865W$

Explanation:

From the question we are told that

Diameter of the cylinder $D=0.3m$

Length of the cylinder $L=1.75m$

Surface temperature of cylinder $T_s=30 \textdegree C=303k$

Speed of air $V=10m/s$

Temperature of air $T=20 \textdegree C$

Generally the equation for Reynolds number is mathematically given by

$Re_D=\frac{VD}{v}$

where

$v=15.27*10^-^6$

$Re_D=\frac{10*0.3}{15.27*10^-^6}$

$Re_D=1.96*10^5$

Generally the equation for Nusselt number is mathematically given by

$N_u=0.6(Re_D)^{0.6}(Pr)^{0.37}$

where

Prandtl number

$Pr=0.71$

$N_u=0.6(Re_D)^{0.6}(Pr)^{0.37}$

$N_u=0.6(1.96*10^5)^{0.6}(0.71)^{0.37}$

$N_u=791.53$

Generally the equation for convective heat transfer is mathematically given by

$h=Nu \frac{k}{D}$

where

$k=25.7*10^{-3}$

$h=791.53*\frac{25.7*10^{-3}}{0.3}$

$h=67.81W/m^2K$

Generally the equation for surface area of a cylinder is mathematically given by

$A=\pi DL$

$A=\pi *0.3*1.75$

$A=1.65m^2$

Generally the equation for convective heat transfer is mathematically given by

$q=h4(T_s-T_{inty)}$

$q=(67.81)*1.65*(30-20)\\$

$q=1118.865W$

3 0

2 years ago