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Old Oct 24th 2009, 06:36 PM   #1
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Several problems..

If anyone could tell me how to solve these I would be very thankful. I am so lost on all of these.

1. Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8 kg mass is another light string which a person uses to pull both blocks horizontally. If the two-block system accelerates a 0.5 m/s^2(squared) then what is the tension in the connecting string between the blocks?

3. A 5X10^3 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T1. Cable 2 applies a force upward and to the left at an angle of 37 degrees to the negative x-axis and has a tension, T2. What is the tension T1?

4. A woman at an airport is pulling a 15kg suitcase with wheels at constant speed by pulling on a strap at an angle θ above the horizontal. She pulls on the strap with a 30.1 N force, and the frictional force is 24 N. What is θ?

5. A shot-putter moves his arm and the 7kg shot through a distance of 1.0 meter. If the shot is given a velocity of 1X10^1 m/s from rest, find the average force exerted on the shot during this time.

6. An ice-skater moving at 1X10^1 m/s coasts to a halt in 1X10^2m on a smoot ice surface. What is the coefficient of friction between the ice and the skates.

7. Find the tension in an elevator cable if the 1001kg elevator is descending with an acceleration of 1.6 m/s^2

8. A 9kg hanging mass is connected by a string over a pulley to a 5kg block sliding on a flat table. If the coefficient of sliding friction is 0.2, find the tension in the string.
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Old Oct 24th 2009, 09:20 PM   #2
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Try and attempt to solve them, and post your attempt. If you are toatally lost on all of these problems, then there seems to be some basic deficiency in fundamental concepts.Go thru the theory again and then try. Also check previous threads in this section.Many similar problems have been solved.
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Old Oct 25th 2009, 03:24 PM   #3
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I would try to attempt them if I had any clue what I was doing. Unfortunately I dont.
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Old Oct 25th 2009, 09:35 PM   #4
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answering in reverse order,
8) m(2)g-T=m(2)a and T- mew m(1)g=m(1)a, solve T, u will get T=m(1)m(2)g(1- mew)/(m1+m2), put values and get answer.
7)T=m(g-a)=8408 newton
6)0=u^2-2(mew g)s get mew=u^2/2gs=.05
5) did not understand the question(if the ans is 350 newton, please reply)
4)Fcos theta=24, put F=30.1 to get cos theta
3)T1=T2 cos theta
T2sin theta=mg solve T1=mg cot theta
1)use free body diagramme on left body (20 kg)
T=20 a=20 * .5=10 newton

Last edited by r.samanta; Oct 25th 2009 at 10:13 PM.
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