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4 years ago

14

You plan a car trip for which you want to average 90 km/h. You cover the first half of the distance at an average speed of only

48 km/h. What must your average speed be in the second half of the trip to meet your goal?

1 answer:

xz_007 [3.2K]4 years ago

7 0

T1=S/V1T2=Ttot-T1=(2S/Vtot)-S/V1V2=S/T2 = S / (2S/Vtot-S/V1)Simplify in V2 = V1Vtot/(2V1-Vtot) = 48 * 90 / 6 = 720 km/hr

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2 years ago

A ladder 7.85 m long leans against the side of a building. If the ladder is inclined at an angle of 79.5° to the horizontal, wha

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4 years ago

a projectile is shot horizontally from the edge of a cliff, 230m above the ground. the projectile lands 300m from base of the cl

bekas [8.4K]

Answer:

The time taken by the projectile to hit the ground is 6.85 sec.

Explanation:

Given that,

Vertical height of cliff = 230 m

Distance = 300 m

Suppose, determine the time taken by the projectile to hit the ground.

We need to calculate the time

Using second equation of motion

$s=ut+\dfrac{1}{2}gt^2$

Where, s = vertical height of cliff

u = initial vertical velocity

g = acceleration due to gravity

Put the value in the equation

$230=0+\dfrac{1}{2}\times9.8\times t^2$

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3 years ago

Does the theory of relativity show that Newtonian mechanics is wrong?

valina [46]

Answer:

Einstein extended the rules of Newton for high speeds. For applications of mechanics at low speeds, Newtonian ideas are almost equal to reality. That is the reason we use Newtonian mechanics in practice at low speeds.

Explanation:

<em>But on a conceptual level, Einstein did prove Newtonian ideas quite wrong in some cases, e.g. the relativity of simultaneity. But again, in calculations, Newtonian ideas give pretty close to correct answer in low-speed regimes. So, the numerical validity of Newtonian laws in those regimes is something that no one can ever prove completely wrong - because they have been proven correct experimentally to a good approximation.</em>

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3 years ago

Assuming 84.0% efficiency for the conversion of electrical power by the motor, what current must the 13.0-V batteries of a 716 k

tino4ka555 [31]

Answer:

$\mathbf{ current(I) =1766.67 \ A}$

Explanation:

Given that:

The air resistance and friction = 700 N

The gravity caused force = 716 × 9.8 = 7016.8

Total force = (7016.8 + 700) N

Total force = 7716.8 N

∴

$13 \times current(I) \times 0.84 = \dfrac{7716.8 \times 300}{2 \times 60}$

$current(I) \times 10.92= 19292$

$current(I) = \dfrac{19292}{10.92}$

$\mathbf{ current(I) =1766.67 \ A}$

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3 years ago