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keziacobham
Mar 2, 2009, 03:20 PM
13. A person weighting 490N stands on a scale in an elevator

(A) What does the scale read when the elevator is at rest?
(B) The elevator ascends, accelerating at 2.7 m/s. What does the scale read?
(C) What is the reading on the scale when the elevator rises at a constant velocity?
(D) The elevator slows down at -2.2m/s ^2 as it reaches the desired floor. What does the scale read?
(E) Suppose the cable snapped and the elevator feel freely. What would the scale read?

14. A horse is pulling a wagon through a rope that mages a 29 degree angle with the ground. The tension of the rope is 430 N.

(A) What is the component of the force parallel to the ground?
(B) If the wagon moves 5.6m, how much work is done by the applied force?
(C) If the wagon moves this distance in 11sec, what power is exerted by the force?
(D) What is the average velocity of the wagon during this time?

15. You place a box weighting 257 N on an inclined plane. As the angle of inclination is changed, the box just begins to move when the plane makes a 38.0 degree angle with the horizontal.

(A) What is the component of the gravitational force acting down the incline plane?
(B) What is the normal force acting on the box?
(C) What is the static friction force just as it is about to begin sliding?
(D) Draw a free body diagram for the box?
(E) What is the coefficient of static friction between the box and the plane?

16. A horse player tosses a horseshoe at an angle of 26.9 above the horizontal over level ground directly toward the stake. The horseshoe has an initial velocity of 12.5m/s

(A) What is the x and y component of the initial velocity?
(B) What is the maximum height reached by the horseshoe?
(C) How long is the horseshoe in the air?
(D) If the stake is 12.0m away from the player, how far from the stake does the horseshoe land?

darkvision
Mar 2, 2009, 04:05 PM
13. A person weighting 490N stands on a scale in an elevator

(A) What does the scale read when the elevator is at rest?
(B) The elevator ascends, accelerating at 2.7 m/s. What does the scale read?
(C) What is the reading on the scale when the elevator rises at a constant velocity?
(D) The elevator slows down at -2.2m/s ^2 as it reaches the desired floor. What does the scale read?
(E) Suppose the cable snapped and the elevator feel freely. What would the scale read?


don't know physics but figured I would have some fun. Lets start with E

firstly what is the distance the elevator is falling? 1 floor or enough floors for terminal velocity to be reached. Secondly, how much friction (resistance) are the rails providing? Thirdly how much air flow(CFM) is around the elevator in the shaft because if the volume around the elevator is low enough the air will be compressed faster than it can escape and therefore slowing the descent.

now for C main one their rising at a constant velocity, well what is the velocity? 25g's .5g's 1g that information greatly matters as the weight of an object differs depending on how much force is being put upon it.

oh and thirdly. Even if I could I wouldn't do your homework for you. :)

sarnian
Mar 3, 2009, 04:39 AM
Hello keziacobham

You have to do your homework yourself. We are here to provide hints or ideas on how you can find the answers yourself.
What are the problems you have with each of these questions?
How far have you come so far? Please state your calculations here, good or fault.

Just as an indication : the elevator question :

You know what happens to yourself when standing in an elevator. When accelerating upwards you feel heavier, and when accelerating downwards you feel lighter. The reverse for decelerating.

A person weighing 490N who stands on a scale in an elevator

(A) weighs 490N when the elevator is at rest
(B) when the elevator starts ascending, you weigh more *
(C) when the elevator rises at a constant velocity you weigh 490N again
(D) when the elevator slows down you weigh less *
(E) if the cable snapped and the elevator falls freely, you fall as fast as the elevator, so you both fall together at the same speed (force = 1 G), and so you seem to weigh nil.

* depending on the acceleration/decelleration - add or deduct the amount of Newton meter