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balandron [24]
3 years ago
5

A car of mass 800 kg is travelling at 30 m/S. The car then brakes suddenly and stops with a braking distance of 75 m find the wo

rk done on the car by the brakes
Physics
1 answer:
gulaghasi [49]3 years ago
4 0

Answer:

-360 kJ

Explanation:

Given:

m = 800 kg

v₀ = 30 m/s

v = 0 m/s

Δx = 75 m

Find: W

We can solve this using either forces or energy.

To use forces, first find the acceleration.

v² = v₀² + 2aΔx

(0 m/s)² = (30 m/s)² + 2a (75 m)

a = -6 m/s²

Then apply Newton's second law:

∑F = ma

F = (800 kg) (-6 m/s²)

F = -4800 N

Work is force times distance:

W = FΔx

W = (-4800 N) (75 m)

W = -360,000 J

W = -360 kJ

If you want to use energy instead:

work = change in energy

W = ΔKE

W = ½mv² − ½mv₀²

W = ½ (800 kg) (0 m/s)² − ½ (800 kg) (30 m/s)²

W = -360,000 J

W = -360 kJ

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The shape is connected in parallel so;

5.1) Ans;

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5.2) Ans;

\frac{1}{R}  =  \frac{1}{R1} +  \frac{1}{R2}   \\  \frac{1}{R}  =  \frac{1}{8}  +  \frac{1}{10}  \\  \frac{1}{R}  =  \frac{5 + 4}{40}  =  \frac{9}{40}  \\ R =  \frac{40}{9}  = 4.4 \:  \: ohm

I hope I helped you^_^

7 0
2 years ago
Reading or writing on a phone is especially dangerous while driving because:
algol [13]

Answer:

Explanation:

When we are driving we need a lot of attention and concentration. Also one involved in driving should be consious and courteous

Thus, whenever a person is drives, and when he is disactracted by Mobile phones it will destroy his presence of mind.

It will good if use mobile after stopping the vehicle

Thanks

5 0
2 years ago
Read 2 more answers
A 94 g particle undergoes SHM with an amplitude of 8.3 mm, a maximum acceleration of magnitude 7.8 x 103 m/s2, and an unknown ph
Lelechka [254]

Answer:

a) T = 6.49*10^-3 s

b) v = 8 m/s

c) E = 3 J

d) F = 733 N

e) F = 366.5 J

Explanation:

Given

Mass of particle, m = 94 g = 0.094 kg

Amplitude of the particle, A = 8.3 mm = 8.3*10^-3 m

Maximum acceleration of particle, a = 7.8*10^3 m/s²

the equation describing Simple Harmonic Motion is given as

x = A cos (wt +φ)

To fond the acceleration of this relationship, we would have to integrate. Twice, the first would be a Velocity, and the second acceleration that we need.

Velocity = dx/dt = -Aw sin(wt + φ)

Acceleration = d²x/dt = -Aw² cos(wt + φ)

From the question, we were given, magnitude of acceleration to be 7.8*10^3 m/s²

Aw² = 7.8*10^3

w² = 7.8*10^3 / A

w² = 7.8*10^3 / 8.3*10^-3

w² = 939759

w = √939759

w = 969

Recall, T = 2π/w, so that

T = (2 * 3.142) / 969

T = 6.49*10^-3 s

Maximum speed = Aw

Maximum speed = 8.3*10^-3 * 969

Maximum speed = 8.0 m/s

Total mechanical energy oscillator =

mgx + 1/2mx² =

1/2mv(max)² =

1/2 * 0.094 * 8² =

3 J

Maximum displacement

x = A cos(wt + φ)

For x to be maximum here, then cos(wt + φ) Must be equal to 1

Acceleration = d²x/dt² = -Aw²

And force = mass * acceleration

Force = 0.094 * 7.8*10^3

Force = 733 N

x = A cos(wt + φ), where cos(wt + φ) = 1/2

d²x/dt² = -Aw² * 1/2

d²x/dt² = 733 * 0.5

= 366.5 N

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The formula used to find potential energy is <em>P.E. = M * G * H</em> (P.E. is potential energy, M is mass, G is gravitational pull, and H is height). So the answer to your question is <em>5 * 9.8 * 2</em>, which equals 98.
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