Quiz
Grade/Cluster
11 ES
Subject
Physics
Section
Date
Name
Duration 20 mins
ID
Score/20
I-Choose the best answer.
[6 marks, 1.5 each]
1. A child with a weight of 4.50 x 102 N sits on a seesaw 0.60 m from the axis of rotation.
How far from the axis of rotation on the other side should a child with a weight of
6.00 x 102 N sit so the seesaw will remain balanced?
√
A.
0.30 m
B.
0.40 m
C.
0.45 m
D.
0.50 m
2. A massless horizontal pole projects a distance r1=1.6 m from the side of a building. It is held up
by a cable running from the side of the building to the end of the pole, making an angle of θ=350 to
the horizontal. A sign weighing W=30 N hangs from the pole a distance r1=1.5 m out from the building.
What is the tension T in the cable?
√
A.
28 N
B.
34 N
C.
39 N
D.
49 N
E.
None of these
1
3. A bucket filled with water has a mass of 23 kg and is attached to a rope that is wound around a
cylinder with a radius of 0.050 m at the top of a well. What torque does the weight of the water and
bucket produce on the cylinder? (g = 9.81 m/s2)
√
A.
34 N.m
B.
11 N.m
C.
17 N.m
D.
23 N.m
4. A 1.0 m long non-uniform plank, shown above, has weight 1000N. It is to be supported by two
rods, A and B, as shown below. The center of mass of the plank is 30 cm from the right edge. Each
support bears half the weight of the plank. If support B is 10 cm from the right-hand edge, how far
from the left-hand edge should support A be?
√
A.
0 cm
B.
10 cm
C.
30 cm
D.
50 cm
E.
70 cm
II- Solve the following problems:
[10 marks]
1. A uniform 5.00 m long horizontal beam that weighs 315 N is attached to a wall by a pin
connection that allows the beam to rotate. Its far end is supported by a cable that makes an
angle of 53° with the horizontal, and a 545 N person is standing 1.50 m from the pin. Find
the force in the cable, FT, and the force exerted on the beam by the wall, R, if the beam is in
equilibrium.
2
Choosin g the pin as the axis of rotation and applying
the sec ond condition of equilibrium,
t net = ( FT sin 53 ´ 5.0) - ( 545 ´1.5) - ( 315 ´ 2.5) = 0
( F sin 53 ´ 5.0) = 817.5 + 787.5
T
1605
= 402N
3.99
Now to find R, we use the first condition of equilibrium.
å Fx = 0
FT =
\ Rx = Fx = F cos53 = 402 cos53 = 242N
& åFy = 0
Ry + Fy = 545 + 315
Ry + F sin 53 = 860N
Ry + 402sin 53 = 860 Þ Ry = 539N
\ R=
( Rx ) + ( Ry )
2
2
=
( 242) + ( 539)
2
2
= 590N
2. A ladder 3 m long and weighing 100 N is leaning against a wall, as shown below. The ladder
makes an angle of 300 to the horizontal. The vertical side of the wall is frictionless, but there
is friction along the floor with maximum ms = 0.2.
A 500 N person is standing on the ladder.
a. Calculate the value of the contact force where the
ladder is touching the wall.
b. How far up the ladder can the person stand before the
ladder will begin to slip.
3
AB = 3.0 cos30 = 2.6m and BC = 3.0sin 30 = 1.5m
( a)
U sin g the 1st condition of equilibrium;
å Fy = 0 Þ N f = 100 + 500 = 600N.
\ Ff = m s N f = 0.2 ´ 600 = 120N
&å Fx = 0 Þ N w = Ff = 120N
( b) U sin g the 2nd condition of equilibrium
and taking torques about point A;
t cw = t ccw
(100 ´1.3) + ( 500 ´ x ) = (120 ´1.5)
Þ x = 0.1m
\d = x cos30 = 0.1cos30 = 0.087m
III- Answer the following questions:
[4 mark]
a. State the two conditions for an object to be in equilibrium. (2 Mark)
First condition: Net force on the object must be zero.
i.e; åF = 0 Þ åFx = 0 and åFy = 0
Second condition: Net torque on an object must be zero.
i.e; åt = 0 Þ åt cw + åt ccw = 0
b. Can an object be in equilibrium when only one force acts on it? Explain. (2 Marks)
No. For an object to be in equilibrium, the net external force acting on it must be zero. This
is not possible when only one force acts on an object.
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5
6
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Quiz (2)
Grade/Cluster
11 ES
Subject
Section
Name
Physics
Date
AK
Duration 20 mins
ID
Score/20
I-Choose the best answer.
[6 marks, 1 each]
1. Which one of the following is not possible value for a charge?
A.
8.0×10-19 C
B.
5.2×10-18 C
C.
6.4×10-18 C
D.
E.
6.4×10-18 C
4.8×10-19 C
2. Which diagram best represents the electric field produced by two oppositely charged particles?
D
8
3. A force of 20 N acts on a charge of 0.5 C in a region of space. The electric field at the point of the charge is
____________________.
A.
10 N/C
B.
100 N/C
C.
160 N/C
D.
E.
40 N/C
0.00625 N/C
4. Two point charges attract each other. The two charges are
A.
both negative
B.
both positive
C.
alike
D.
unlike
E.
equal
5. In the figure below, rank with the largest first the magnitudes of the electric field at points A, B, and C.
A.
A, B, C
B.
A, C, B
C.
C, A, B
D.
B, C, A
E.
The answer cannot be determined by visual inspection
9
6. The electrostatic force between two charges is 54 N when they are 2 cm apart. What will the value of this
force be if the charges are moved to a new separation of 6 cm?
A.
3N
B.
6N
C.
18 N
D.
162 N
E.
486 N
II- Solve the following problems:
[11 marks]
7. A student sits on a pivoted stool while holding a pair of weights as in the figure below. The stool is free to
rotate about a vertical axis with negligible friction. The moment of inertia of student, weights, and stool is
3.25 kg. m2. The student is set in rotation with arms outstretched, making one complete turn every 1.5 s. As
he rotates, he pulls the weights inward so that the new moment of inertia of the system (student, weights,
and stool) becomes 2.80 kg. m2. What is the new angular speed of the system? ( 3 marks )
8. Three charges lie along the x-axis as in the figure below. The positive charge =1.50 μC is at x = 3.0
cm, and the positive charge =6.00 μC is at the origin. Where a negative charge q3 must be placed on
the x-axis so that the resultant electric force on it is zero? (3 marks)
10
9. Two charges 1 q =5.0 μC, and a negative charge 2 q =−2.0 μC are 1 m away from each other
as shown in the figure. Determine the electric field magnitude and direction at the
midpoint M. ( 5 marks )
III- Answer the following questions:
[3 marks]
10. In the figure shown below, what is the ratio of q1 to q2?
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