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densk [106]
3 years ago
8

A 1000 kg car is rolling slowly across a level surface at 1m/s, heading toward a group of small innocent children.

Physics
2 answers:
Ne4ueva [31]3 years ago
7 0

Answer:

The force is -1620.73 N.

Explanation:

Given that,

Mass of car = 1000 kg

Velocity = 1 m/s

Distance = 2 m

Angle = 30°

We need to calculate the force

Using formula of work done

W_{net}=K_{f}-K_{i}

F\times d=K_{f}-K_{i}

Fd\cos\theta=-K_{i}

F=\dfrac{-K_{f}}{d\cos\theta}

F=-\dfrac{\dfrac{1}{2}mv^2}{d\cos\theta}

Put the value into the formula

F=-\dfrac{\dfrac{1}{2}\times1000\times(1)^2}{2\times\cos30}

F=-1620.73\ N

Hence, The force is -1620.73 N.

AnnyKZ [126]3 years ago
4 0

Answer:

Force, F = 288.67 N

Explanation:

Mass of the car, m = 1000 kg

Initial speed of the car, u = 1 m/s

The car and push on the hood at an angle of 30° below horizontal, \theta=30^{\circ}

Distance, d = 2 m

Let F is the force must you push to stop the car. using work energy theorem to find it. According to this theorem, the work done is equal to the change in kinetic energy as :

W=\dfrac{1}{2}m(v^2-u^2)

F\times d=\dfrac{1}{2}m(v^2-u^2)

It stops, v = 0

Fd\ cos\theta=\dfrac{1}{2}m(u^2)      

F=\dfrac{\dfrac{1}{2}m(u^2)}{d\ cos\theta}

F=\dfrac{\dfrac{1}{2}\times 1000\times (1)^2}{2\ cos(30)}

F = -288.67 N

So, the force required to push to stop the car is 288.67 N. Hence, this is the required solution.                                            

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Given Information:

Frequency of horn = f₀ = 440 Hz

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Answer:

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Case 2. When the bus is approaching the student = 414.9 Hz

Case 3. When the bus is moving away from the student = 468.4 Hz

Explanation:

There are 3 cases in this scenario:

Case 1. When the bus is crossing the student

Case 2. When the bus is approaching the student

Case 3. When the bus is moving away from the student

Let us explore each case:

Case 1. When the bus is crossing the student:

Student will hear the same frequency emitted by the horn that is 440 Hz.

f = 440 Hz

Case 2. When the bus is approaching the student

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f = 440 ( 0.943 )

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Case 3. When the bus is moving away from the student

f = f₀ ( v / v+v₀ )

f = 440 ( 330/ 330-20 )

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