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3 years ago

A 4,000-kg car traveling at 20m/s hits a wall with a force of 80,000 N and comes to a stop. What was the impact time?

1 answer:

Nookie1986 [14]3 years ago

7 0

Rate of change of momentum = impact force
(m*v-m*u)/t = F
4000*20/t = 80000 (note: v is zero as it stopped)
<span>soo, t = 1 sec</span>

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A roller coaster is released from the top of a track that is 57 m high. Find the roller coaster speed when it reaches ground lev

Art [367]

Hi there!

Assuming the track is frictionless:

$E_i = E_f\\\\PE = KE\\\\mgh = \frac{1}{2}mv^2$

Cancel out the masses and rearrange to solve for velocity:

$gh = \frac{1}{2}v^{2}\\\\v = \sqrt{2gh}\\\\$

Plug in the given height and let g = 9.8 m/s²:

$v = \sqrt{2(9.8)(57)} = \boxed{33.42 m/s}$

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2 years ago

Electrical energy is used to turn the blades of a fan. The amount of energy transformed is seen here : 750 J electrical energy i

Charra [1.4K]

Electrical energy is used to run the fan

Here as per given condition 750 J of electrical energy is used to run the fan which is converted into Kinetic energy as 400 J

So here we can see that 350 J of energy is lost against many other type of frictional and resistive loses.

So here we can say that out of 750 J of energy only 400 J is used to run the fan and rest amount of energy is lost against friction.

also we can say that efficiency of this fan will be

$\eta = \frac{Useful}{Total}$

$\eta = \frac{400}{750}$

$\eta = \frac{8}{25}$

3 0

3 years ago

In the first stage of a two-stage Carnot engine, energy is absorbed as heat Q1 at temperature T1 = 500 K, work W1 is done, and e

Nataly [62]

Answer:

Efficiency = 52%

Explanation:

Given:

First stage

heat absorbed, Q₁ at temperature T₁ = 500 K

Heat released, Q₂ at temperature T₂ = 430 K

and the work done is W₁

Second stage

Heat released, Q₂ at temperature T₂ = 430 K

Heat released, Q₃ at temperature T₃ = 240 K

and the work done is W₂

Total work done, W = W₁ + W₂

Now,

The efficiency is given as:

$\eta=\frac{\textup{Total\ work\ done}}{\textup{Energy\ provided}}$

Work done = change in heat

thus,

W₁ = Q₁ - Q₂

W₂ = Q₂ - Q₃

Thus,

$\eta=\frac{(Q_1-Q_2)\ +\ (Q_2-Q_3)}{Q_1}}$

$\eta=1-\frac{(Q_1-Q_3)}{Q_1}}$

$\eta=1-\frac{(Q_3)}{Q_1}}$

also,

$\frac{Q_1}{T_1}=\frac{Q_2}{T_2}=\frac{Q_3}{T_3}$

$\frac{T_3}{T_1}=\frac{Q_3}{Q_1}$

thus,

$\eta=1-\frac{(T_3)}{T_1}}$

thus,

$\eta=1-\frac{(240\ K)}{500\ K}}$

$\eta=0.52$

Efficiency = 52%

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3 years ago

The acceleration of a train moving from rest and its speed reaches 36m/sec in 9 sec

jenyasd209 [6]

Answer:

4 m/s^2

Explanation:

The acceleration is defined as: Δv/Δt (the difference of the velocity over a time period in which happens that difference).

Remember that a difference is calculated by subtracting the initial value of a physical quantity from its final value.

In our case:

Δv = Vfinal - Vinitial = 36m/s - 0 m/s = 36m/s

Δt = 9s

a = Δv/Δt = 36m/s / 9s = 4m/s^2

4 0

2 years ago

Help meee!! PLZZZZ It's worth 20 points and if you get it right I will mark brainlist.

professor190 [17]

Answer: I Think it should be Mixture.

Explanation: Because titanium is a mixture and its only 1% of the 2nd option and its not a pure substance and it might be a compound.

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2 years ago