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3 years ago

9

Driving at 75m/s, you hit the brakes on your new car, accelerating at a rate of -20m/s. How long will it take the car to come to

rest?

1 answer:

soldi70 [24.7K]3 years ago

5 0

Answer:

3.75s

Explanation:

Using equation of motion, t= (v-u)/a

where v=0, u=75 and a=-20

t=-75/-20=75/20=3 /.75

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A car of mass 750 kg accelerates away from traffic lights. At the end of the first 100 m it has reached a speed

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the work done on the car by the force of its engine is 78,000 J.

" The work done on the car by the force of friction is 24,000 J.

Increasing the car's kinetic energy at the end of the first 100 m is 54,000J

a. Completed work = force x distance. Engine output = 780 N, that is,

780 N x 100 m = 78,000 J.

b. Completed work = force x distance. Friction force = 240 N, that is,

240 N x 100 m = 24,000 J.

c. Kinetic energy = 1 \ 2 x m x v2

= 1 \ 2 x 750 kg x 12 squared = 375 x 144 = 54,000 J.

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2 years ago

Which one is it? Help ASAP

dezoksy [38]

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extreme heat, because no physical damage can demagnetize a magnet

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3 years ago

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You wiggle a string,that is fixed to a wall at the other end, creating a sinusoidalwave with a frequency of 2.00 Hz and an ampli

FinnZ [79.3K]

Answer:

Explanation:

A general wave function is given by:

$f(x,t)=Acos(kx-\omega t)$

A: amplitude of the wave = 0.075m

k: wave number

w: angular frequency

a) You use the following expressions for the calculation of k, w, T and λ:

$\omega = 2\pi f=2\pi (2.00Hz)=12.56\frac{rad}{s}$

$k=\frac{\omega}{v}=\frac{12.56\frac{rad}{s}}{12.0\frac{m}{s}}=1.047\ m^{-1}$

$T=\frac{1}{f}=\frac{1}{2.00Hz}=0.5s\\\\\lambda=\frac{2\pi}{k}=\frac{2\pi}{1.047m^{-1}}=6m$

b) Hence, the wave function is:

$f(x,t)=0.075m\ cos((1.047m^{-1})x-(12.56\frac{rad}{s})t)$

c) for x=3m you have:

$f(3,t)=0.075cos(1.047*3-12.56t)$

d) the speed of the medium:

$\frac{df}{dt}=\omega Acos(kx-\omega t)\\\\\frac{df}{dt}=(12.56)(1.047)cos(1.047x-12.56t)$

you can see the velocity of the medium for example for x = 0:

$v=\frac{df}{dt}=13.15cos(12.56t)$

7 0

3 years ago

What volume will be occupied by 20g of Copper if the density of Copper is 9.1g/ml?

Eva8 [605]

Answer:

The volume of copper is 2.198 ml

Explanation:

Given;

mass of copper, m = 20 g

density of copper, ρ = 9.1 g/ml

Density is given by;

Density = mass / volume

Volume = mass / density

Volume = (20 g) / (9.1 g/ml)

Volume = 2.198 ml

Therefore, the volume of copper is 2.198 ml

3 0

3 years ago