Faculty of Science, Physics Dept
Course Name: Physics (1)
Course Code: PHYS 103
Academic Year: 1st Term 2025
Deadline: 31/10/2025
Homework 1
Student Name::
Student Academic Number::
Student Section::
Important Information
• Organize your work, in a reasonably neat and coherent way, in the space provided.
Work scattered all over the page without a clear ordering will receive very little credit.
• Mysterious or unsupported answers will not receive full credit. A correct answer,
unsupported by calculations, explanation, or algebraic work will receive no credit;
an incorrect answer supported by substantially correct calculations and explanations
might still receive partial credit.
• If you miss your deadline,(31/10/2025) at 23:59, you will not be allowed and the
marks will be given zero.
Answer all the following questions:
1. Two objects are connected by a light string that passes over a frictionless pulley as shown
in Figure below. Assume the incline is frictionless and take m1 = 2 kg, m2 = 6 kg, and
θ = 55◦ .
(a) Draw free-body diagrams of both objects.
(b) Find the magnitude of the acceleration of the objects.
(c) Find the tension in the string.
(d) Find the speed of each object t=2s after it is released from rest.
2. An object of mass m1 = 5 kg placed on a frictionless, horizontal table is connected to a
string that passes over a pulley and then is fastened to a hanging object of mass m2 = 9
kg as shown in Figure below
(a) Draw free-body diagrams of both objects.
(b) Find the magnitude of the acceleration of the objects.
(c) Find the tension in the string.
3. A 5 kg block is placed on top of a 10 kg block (Fig. below). A horizontal force of 45 N
is applied to the 10 kg block, and the 5 kg block is tied to the wall. The coefficient of
kinetic friction between all moving surfaces is 0.2.
(a) Draw a free-body diagram for each block and identify the actionâĂŞreaction forces
between the blocks.
(b) Determine the tension in the string.
(c)the magnitude of the acceleration of the 10 kg block.
4. A block of mass mt = 4 kg is put on top of a block of mass mb = 5 kg. To cause the
top block to slip on the bottom one while the bottom one is held fixed, a horizontal
force of at least 12 N must be applied to the top block. The assembly of blocks is now
placed on a horizontal, frictionless table as shown below. Find the magnitudes of (a) the
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maximum horizontal force F that can be applied to the lower block so that the blocks
will move together and (b) the resulting acceleration of the blocks.
5. A setup similar to the one shown in Figure below is often used in hospitals to support
and apply a horizontal traction force to an injured leg.
(a) Determine the force of tension in the rope supporting the leg.
(b) What is the traction force exerted to the right on the leg?
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6. Figure below, blocks A and B have weights of 44 N and 22 N, respectively. (a) Determine
the minimum weight of block C to keep A from sliding if μs between A and the table
is 0.20. (b) Block C suddenly is lifted off A. What is the acceleration of block A if μk
between A and the table is 0.15?
7. An amusement park ride consists of a rotating circular platform 8 m in diameter from
which 10 kg seats are suspended at the end of 2.5 m massless chains as shwon in Fig.
below. When the system rotates, the chains make an angle θ = 28◦ with the vertical.
(a) What is the speed of each seat?
(b) Draw a free-body diagram of a 40 kg child riding in a seat and find the tension in
the chain.
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8. A person stands on a scale in an elevator. As the elevator starts, the scale has a constant
reading of 591 N. As the elevator later stops, the scale reading is 391 N. Assuming the
magnitude of the acceleration is the same during starting and stopping, determine:
(a) the weight of the person.
(b) the personâĂŹs mass.
(c) the acceleration of the elevator.
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9. A force F applied to an object of mass m1 produces an acceleration of 3m/s2 . The same
force applied to a second object of mass m2 produces an acceleration of 1m/s2 .
(a) What is the value of the ratio m1 /m2 ?
(b) If m1 and m2 are combined into one object, find its acceleration under the action of
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the force F .
10. An elevator cab that weighs 27.8 kN moves upward.What is the tension in the cable if
the cabâĂŹs speed is (a) increasing at a rate of 1.22 m/s2 and (b) decreasing at a rate
of 1.22 m/s2 ?
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