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Lyzinski Physics
Tension Problems
1) A Train is being pulling three cars of masses 5,000 kg, 6000 kg, and 8000 kg behind it,
in this order. The locomotive is directly coupled to the 5,000 kg car, which it pulls
with a force of 50,000 N. Determine the force in the couplings between the cars if…
a) The track is frictionless.
b) The track has a coefficient of friction of 0.15
8,000 kg
Car 3
6,000 kg
5,000 kg
Car 2
Car 1
2) A 40 kg block on a level, frictionless table is connected to a 15 kg
mass by a rope passing over a frictionless pulley. What will be
the acceleration of the 15 kg mass when it is released?
3) A 5.0 kg mass rests on a level, frictionless table, attached to a 3.0
kg mass by a light string that passes over a frictionless pulley. Calculate the tension in
the string when the masses are released.
4) A 3.0 kg mass is attached to a 5.0 kg mass by a strong string that passes
over a frictionless pulley. When the masses are allowed to hang
freely, what will be:
5.0 kg
a) the acceleration of the masses, and
b) the magnitude of the tension in the string?
c) the force in the bracket (while the blocks are in motion) that
attaches the pulley to the ceiling
5) A 50kg box is pushed by a 600N force into a 30 kg box. The coefficient of friction
between the boxes is 0.1. Find the action/reaction forces between the boxes.
6) A 0.10 g spider is descending on a strand that supports it with a force of 5.6 x 10–4 N.
What is the acceleration of the spider? Ignore the factor of air resistance.
7) A 5000 kg helicopter accelerates upward at 0.50 m/s2 while lifting a 2000 kg car.
a) What is the lift force exerted by the air on the rotors?
b) What is the tension in the cable that connects the car to the helicopter?
(hint: draw an accurate FBD for each object and use Newton’s 2nd Law)
3.0 kg
8) For each FRICTIONLESS system, find the acceleration of the masses.
200 g
4.0 kg
1.0 kg
100 g
2.0 kg
(a)
(b)
3.2 kg
200 g
(c)
9) Two masses are connected by a light cord over a frictionless pulley, as illustrated. If the
coefficient of kinetic friction is 0.18, what is:
5.0 kg
a) the acceleration of the system, and
b) the tension in the cord? Assume that the system starts to move.
c) for what values of µs will the block not start?
3.2 kg
10) Using the frictionless inclined system below,
a) what is the acceleration of the blocks and the tension in the rope?
b) what is the minimum coefficient of friction (if there were friction) that would keep
the blocks at rest?
7.0 kg
3.0 kg
30o
11) What is the acceleration of the system illustrated, if the coefficient of kinetic friction is
0.20? Assume that it starts.
4.0 kg
30o
Answers
1a)
1b)
2)
3)
4)
5)
a=2.63 m/s2; 21,053 N; 36,842 N
a=1.16 m/s2; 21,053 N; 36,842 N
2.7 m/s2
18 N
2.5 m/s2; 37 N; 73.5 N
225 N
3.0 kg
Hint: Figure out
which way it would
go first, so that you
know which direction
friction acts!
6) 4.2 m/s2, down
7) 7.2 x 104 N, up; 20,600 N
8) 2.0 m/s2, 2.3 m/s2, 2.0 m/s2
9) 2.7 m/s2, 23 N,  .64
10) .49 m/s2 downhill, 31N, .08
11) .43 m/s2 uphill