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3 years ago

a train starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of 24 m/s.

Physics

1 answer:

Xelga [282]3 years ago

7 0

My best guess would be 50.4 hope im right

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id.k

Explanation:

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3 years ago

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3 years ago

Suppose a police officer is 1/2 mile south of an intersection, driving north towards the intersection at 40 mph. At the same tim

blagie [28]

Answer:

75.36 mph

Explanation:

The distance between the other car and the intersection is,

$x=x_{0}+V t \\ x=\frac{1}{2}+V t$

The distance between the police car and the intersection is,

$y=y_{0}+V t$

$y=\frac{1}{2}-40 t$

(Negative sign indicates that he is moving towards the intersection)

Therefore the distance between them is given by,

$z^{2}=x^{2}+y^{2}(\text { Using Phythogorous theorem })$

$z^{2}=\left(\frac{1}{2}+V t\right)^{2}+\left(\frac{1}{2}-40 t\right)^{2} \ldots \ldots \ldots(1)$

The rate of change is,

$2 z \frac{d z}{d t}=2\left(\frac{1}{2}+V t\right) V+2\left(\frac{1}{2}-40 t\right)(-40)$

$2 z \frac{d z}{d t}=V+2 V^{2} t-40+3200 t \ldots \ldots \ldots$

Now finding $z$ when $t=0,$ from (1) we have

$z^{2}=\left(\frac{1}{2}+V(0)\right)^{2}+\left(\frac{1}{2}-40(0)\right)^{2}$

$z^{2}=\frac{1}{4}+\frac{1}{4}=\frac{1}{2} \\ z=\sqrt{\frac{1}{2}} \approx 0.7071$

The officer's radar gun indicates 25 mph pointed at the other car then, $\frac{d z}{d t}=25$ when $t=0,$ from

From (2) we get

$2(0.7071)(25)=V+2 V^{2}(0)-40+3200(0)$

$2(0.7071)(25)=V+2 V^{2}(0)-40$

$35.36=V-40$

$V=35.36+40=75.36$

Hence the speed of the car is $75.36 mph$

7 0

3 years ago

A carpenter lifts a 10-kg piece of wood to his shoulder 1.5 m above the ground. He then sets the wood on his truck at 1.0 m abov

FinnZ [79.3K]

Answer:

<em>500Joules</em>

Explanation:

Kinetic energy = 1/2mv²

m is the mass of the wood

v is the velocity

Given

Mass = 10kg

Velocity v = 10m/s

Substitute into the formula and get KE

KE = 1/2 * 10 * 10²

KE = 1/2 * 1000

KE = 500Joules

<em>Hence the kinetic energy of the wood during delivery is 500Joules</em>

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3 years ago

• Can you explain why scientific theories will change over time?

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Because as we develope into our times from today to tomorrow and the next, us as a human race will never stop discovering

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