Physics, 15.11.2019 05:31 deanlmartin

An elevator is rising at constant speed. consider the following statements: i. the upward cable force is constant ii. the kinetic energy of the elevator is constant iii. the gravitational potential energy of the earth-elevator system is constant iv. the acceleration of the elevator is zero v. the mechanical energy of the earth-elevator system is constan

Answers: 2

Show answers

Answers

Answer from: angvtl02

I True

II True

III False

IV True

V False

Explanation:

I. the upward cable force is constant

True. As the elevator is rising at constant speed. According to Newton's first law, the net force acting on it must be zero. Vertically there are 2 forces at play here: gravity and the cable tension. They are equal and opposite. Since mass is unchanged, gravity is unchanged, so is the tension force.

II. the kinetic energy of the elevator is constant

True. Since $E_k = \frac{mv^2}{2}$ . Mass is constant, speed is constant. Then the kinetic energy must be constant.

III. the gravitational potential energy of the Earth-elevator system is constant

False. As the elevator is rising, its height with respect to a reference system is increasing. and E_p = mgh . So the gravitational potential energy must be changing too.

IV. the acceleration of the elevator is zero

True. Since speed is constant. And acceleration is change of speed over time. Acceleration must be 0 here.

V. the mechanical energy of the Earth-elevator system is constant

False as the elevator is withdrawing energy from external and converting to potential energy for it to rise. Total Mechanical energy must be rising as well.

Answer from: emilylunaa

I, II & IV are true

III & V are not true

Explanation:

TRUE STATEMENTS

I) At constant speed, constant mass and given that acceleration due to gravity is also constant, the upward cable force is constant.

II) K.E is given by $\frac{1}{2} mv^{2}$

at constant mass and constant velocity (speed), the K.E of the elevator is constant.

IV) Acceleration is given by change in speed over a given time, i a system where the speed is constant i.e. initial speed = final speed, change in speed is zero (0) and as such, acceleration is zero.

FALSE STATEMENTS

III) There is constant gravitational work done to resist the upward movement of the system and the energy expended for this work increases as the elevator goes higher (P.E = mgh), as such, gravitational P.E is not constant.

V) The elevator system has a constant Kinetic energy, however the potential energy increases with height and as such, the mechanical energy of the system is not constant.

Answer from: Quest

Ibelieve your answer is b.hope this : )

Answer from: Quest

im guessing the west of station b

Another question on Physics

Physics, 22.06.2019 04:00

10 newton object is placed 3 meters from the fulcrum. at what distance on the other side would you need to place a 15 newton object to balance the lever? show your work!

Answers: 2

Answer

Physics, 22.06.2019 04:10

An initially unpolarized light if intensity 500 w/m^2 passes through four polarizers. the transmission axis between adjacent polarizers is 45∘. what percentage of the initial intensity is transmitted by the system?

Answers: 2

Answer

Physics, 22.06.2019 05:00

Unpolarized light falls on two polarizer sheets whose transmission axes are at right angles. a third polarizer is placed between the first two so that its axis makes a 52-degree angle with the axis of the first polarizer. a) what fraction of the incident light intensity is transmitted through the first polaroid? b) what fraction of the incident light intensity is transmitted through the second polaroid? c) what is the angle of polarization of the light that enters the third polaroid? d) what fraction of the incident light intensity is transmitted through the third polaroid. e) what happens if the middle polaroid is removed?

Answers: 3

Answer

Physics, 22.06.2019 06:30

The energy of a photon was found to be 3.38 × 10–19 j. planck’s constant is 6.63 × 10–34 j • s. which color of light corresponds to this photon?

Answers: 2

Answer

You know the right answer?

An elevator is rising at constant speed. consider the following statements: i. the upward cable for...

Questions