PHYSICS COLLEGE

1. Towards the end of a 400m race, Faisal and Edward are leading and are both running at 6m/s. While Faisal is 72m from the finish line Edward is 100m from the finish line. Realising this and to beat Faisal, Edward decides to accelerate uniformly at 0.2 m/s2 until the end of the race while Faisal keeps on the same constant speed. Does Edward succeed in beating Faisal?

Answers

Answer 1
Answer:

Answer:

  no

Explanation:

Faisal will finish the race in ...

  (72 m)/(6 m/s) = 12 s

In order to beat Faisal, Edward's average speed in those 12 seconds must exceed ...

  (100 m)/(12 s) = 8 1/3 m/s

To achieve that average speed, Edward's acceleration must be ...

  (8 1/3 m/s -6 m/s)/(12 s/2) = 7/18 m/s² ≈ 0.3889 m/s²

Accelerating at only 0.2 m/s², Edward will not beat Faisal.

_____

Additional comment

When acceleration is uniform, the average speed is reached halfway through the period of acceleration.

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Energy is the capacity to do work, but not to produce heat

The following three appliances are connected to a 120 volt house circuit: (i) a toaster, 1200 Watts, (ii) a coffee pot, 750 Watts, and (iii) a microwave, 600 Watt. If all operate at the same time, what total current would they draw

Answers

Answer:

They would draw a total of 21.25 amperes

Explanation:

The total power consumed is

1200 W+ 750 W + 600 W= 2550 Watts

The formula relating the power consumed, the voltage and the current is given as

P=IV---------------1

given that the voltage supply is 120V

2550=I*120\n\I=(2550)/(120) \n\nI= 21.25amps

The triceps muscle in the back of the upper arm extends the forearm. This muscle in a professional boxer exerts a force of 2.00 x 103N with an effective perpendicular arm of 3.0 cm, producing an angular acceleration of the forearm of 130 rad/s2

What is the moment of inertia of the boxer's forearm?

Answers

To solve this problem it is necessary to apply the concepts related to Torque as a function of Force and distance. Basically the torque is located in the forearm and would be determined by the effective perpendicular lever arm and force, that is

\tau = F * r

Where,

F = Force

r = Distance

Replacing,

\tau = 2*10^3*0.03

\tau = 60N\cdot m

The moment of inertia of the boxer's forearm can be calculated from the relation between torque and moment of inertia and angular acceleration

\tau = I \alpha

I = Moment of inertia

\alpha = Angular acceleration

Replacing with our values we have that

I = (\tau)/(\alpha)

I = (60)/(120)

I = 0.5kg\cdot m^2

Therefore the value of moment of inertia is 0.5kg\cdot m^2

A piston-cylinder device initially contains 1.4 kg saturated liquid water at 200oC. Now heat is transferred to the water until the volume quadruples and the cylinder contains saturated vapor only. Determine (a) the volume of the cylinder, (b) the final temperature.

Answers

Answer:

Explanation:

Given

mass of saturated liquid water m=1.4\ kg

at 200^(\circ) specific volume is \nu =0.001157\ m^3\kg(From Table A-4,Saturated water Temperature table)

V_1=m\nu _1

V_1=1.4* 0.001157

V_1=1.6198* 10^(-3)\ m^3

Final Volume V_2=4V_1

V_2=4* (1.6198* 10^(-3))

V_2=6.4792* 10^(-3)\ m^3

Specific volume at this stage

\nu _2=(V_2)/(m)

\nu _2=(6.4792* 10^(-3))/(1.4)

\nu _2=0.004628\ m^3/kg

Now we see the value and find the temperature it corresponds to specific volume at vapor stage in the table.

T_2=T_1^(*)+(T_2^(*)-T_1^(*))/(\alpha _2^(*)-\alpha _1^(*))* (\alpha _2-\alpha _1^(*))

T_2=370^(\circ)+(373.95-370)/(0.003106-0.004953)* (0.004628-0.004953)

T_2=370.7^(\circ) C

Final answer:

The problem in the question is solved using the principles of thermodynamics. The volume of the device after the heat transfer is 6311.2 cm³. The final temperature inside the cylinder, when the water reached the state of saturated vapor, is approximately 240°C.

Explanation:

The subject question is a thermodynamics problem; more specifically dealing with changes of state, volume, and temperature in a system under certain conditions.

For solving part (a), one would first need to find the specific volume (v) at the initial state, which is saturated liquid at 200°C. Looking up in the property tables, we see that v = 1.127 cm³/g for saturated water at 200°C. Then, the initial volume (V) is mass times specific volume, so V = 1.4 kg x 1.127cm³/g x 1000g/kg = 1577.8 cm³. Because volume quadrupled, the final volume is 4 x 1577.8 cm³ = 6311.2 cm³.

For part (b), at the final state, the water is a saturated vapor. The specific volume at the final state is the final volume divided by the mass, which equals to 6311.2 cm³ / 1.4kg / 1000g/kg = 4.507 cm³/g. Look this value up in the property table to find the corresponding temperature. We get a final temperature of about 240°C.

Learn more about Thermodynamics here:

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Ken Griffey, Jr's warehouse shot in the 1933 home run derby travelled 93 feet per second for 5 seconds. How far did he hit the ball?

Answers

Answer:

465 feet because 93*5 = 465, btw that was 1993 not 1933

Explanation:

A proton with a velocity in the positive x-direction enters a region where there is a uniform magnetic field B in the positive y-direction. You want to balance the magnetic force with an electric force so that the proton will continue along a straight line. The electric field should be in the ______ direction.

Answers

Answer:

Negative z-direction.

Explanation:

We need to determine the direction of the magnetic force. Since the velocity of the proton is in the positive x direction, and the magnetic field is in the positive y direction, we know by the vectorial formulaF=q(v* B) (or, alternatively, with the left hand rule) that the magnetic force points in the positive z-direction (also taking into account that the charge is positive), so the electric field should be in the negative z-direction to balance it.

Which of the following statements are true?A. The decrease in the amplitude of an oscillation caused by dissipative forces is called damping. B. The increase in amplitude of an oscillation by a driving force is called forced oscillation. C. In a mechanical system, the amplitude of an oscillation diminishes with time unless the lost mechanical energy is replaced. D. An oscillation that is maintained by a driving force is called forced oscillation.

Answers

Statements that are right as regards oscillation are:

A. The decrease in the amplitude of an oscillation caused by dissipative forces is called damping.

B. The increase in amplitude of an oscillation by a driving force is called forced oscillation.

C. In a mechanical system, the amplitude of an oscillation diminishes with time unless the lost mechanical energy is replaced.

D. An oscillation that is maintained by a driving force is called forced oscillation.

  • Amplitude can be regarded as magnitude of change that is been experienced by oscillating variable with each oscillation.

  • When there is a decrease in the amplitude of an oscillation as a result dissipative forces, then it is regarded as damping.

  • When there is increase in amplitude of an oscillation as a result of driving force then it is termed  forced oscillation.

Therefore, the options are correct.

Learn more at:

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Answer:

right A, B, C, D

Explanation:

They ask which statements are true

A) Right. The decrease in amplitude is due to the dissipation of energy by friction and is called damping

B) Right. In resonant processes the amplitude of the oscillation increases, being a forced oscillation

C) Right. In a system with energy loss, the amplitude must decrease, therefore energy must be supplied to compensate for the loss.

D) Right. It is a resonant process the driving force keeps the oscillation of the system
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