# physics

A lamp hangs vertically from a cord in a descending elevator that declerates at 2.4m/s^2 a) if the tension in the cord is 89N what is the lamp's mass? b) what is the cord's tension when the elevator is ascends with an upward acceleration of 2.4m/s^2?

I know T=w where w=mg. Would I use T-mg=ma? I should be getting 31.3 kN for a) and 24.3kN for part b but I can't figure out my problem.

Yes, use
T - mg = ma.
T does NOT equal mg when the elevator is accelerating or decelerating.

In the first case,
89 N = m (g + a)
m = 89/(9.8 + 2.4) = 7.3 kg
I used a plus sign for "a" since it is decelerating and descending

The (a) problem asks for a mass, so I don't see how the answer can be in Newtons.

1. 👍 0
2. 👎 0
3. 👁 132
1. Acceleration used should be -2.4.
If you used acceleration as +2.4, the tension should be negative according to its free diagram
mg-t=ma , which yields to 12.02 kg

1. 👍 0
2. 👎 0
posted by P6

## Similar Questions

1. ### Physics

A lamp hangs vertically from a cord in a descending elevator with a constant deceleration a. If the tension in the cord is T0, answer the following. (Use any variable or symbol stated above along with the following as necessary:

asked by Rachel on February 11, 2013
2. ### Physics

A lamp hangs vertically from a cord in a descending elevator that decelerates at 2.9 m/s2. a) If the tension in the cord is 94 N, what is the lamp's mass? b)What is the cord's tension when the elevator ascends with an upward

asked by Aalaa on October 8, 2012
3. ### physics

A lamp hangs vertically from a cord in a descending elevator that decelerates at 2.6 m/s2. (a) If the tension in the cord is 54 N, what is the lamp's mass? (b) What is the cord's tension when the elevator ascends with an upward

asked by Rebekah on October 4, 2011
4. ### physics

A weight is hung by a cord from the ceiling of an elevator. From the following conditions, choose the one in which the tension of the cord would be the greatest...least?(draw force diagrams) a) elevator descending at a decreasing

asked by Jamie Lynn on December 17, 2008
5. ### Physics

A 18.6 kg monkey hangs from a cord suspended from the ceiling of an elevator. The cord can withstand a tension of 202 N and breaks as the elevator accelerates. What was the elevator's minimum acceleration? (in m/s^2)

asked by Tanner on February 11, 2015
6. ### PHYSICS 2

A 15.7 kg monkey hangs from a cord suspended from the ceiling of an elevator. The cord can withstand a tension of 240 N and breaks as the elevator accelerates. What was the elevator's minimum acceleration? (Assume the positive

asked by Ellie Mae on October 9, 2006
7. ### phys sci..

A 12.5kg monkey hangs from a cord suspended from the ceiling of an elevator. The cord can withstand a tension of 157N and breaks as the elevator accelerates. What was the magnitude of the elevator's minimum acceleration? What was

asked by Dione on October 2, 2009
8. ### Science

A lamp is suspended by a massless string from the ceiling of a descending elevator which decelerates at 1.6 m/s2. If the tension in the string is 82.0 N, what is the mass of the lamp?

asked by Mark on October 25, 2011
9. ### Physics

A 17.0 kg monkey hangs from a cord suspended from the ceiling of an elevator. The cord can withstand a tension of 220N and breaks as the elevator accelerates. What was the elevator's minimum acceleration (magnintude and

asked by Kelly on January 2, 2007
10. ### Science

An existing cord that you use for a lamp is much thinner than an extension cord recommended for use with large appliances. if u plugged in a refrigerator using a lamp extension cord, the plastic coating of the cord could melt and

asked by Albert Einstein on May 3, 2015

More Similar Questions