Term-3 Quiz 1: Impulse and Momentum
Grade/Cluster
11 Core
Subject
Physics
Section
Date
Name
Duration 25 minutes
ID
Score/25
I-Choose the best answer
[5 marks, 1 each]
1. Which one of the following statements is true?
A.
Momentum is a force.
B.
Momentum is a scalar quantity.
C.
The momentum of an object is always positive.
D.
the impulse on an object is equal to the change in momentum it causes
Momentum is the average force and the time interval over which it acts
E.
2. On a force-time graph, the area under the graph is a measure of ….
A.
Force
B.
Mass
C.
Impulse
D.
work done
E.
Momentum
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3. A force acts on a mass as shown in the force vs time graph
The change in momentum of the mass between 2s and 5s is…
A.
9kg.m/s
B.
18kg.m/s
C.
21kg.m/s
D.
30kg.m/s
E.
42kg.m/s
4. A 945-kg car is moving along a straight highway with a speed of 98 km/h. The driver applies
the brakes and reduces the car's speed to 36 km/h in 8.5 s. What is the impulse on the car?
A.
-1.9×103 N · s
B.
-6.9×103 N · s
C.
-1.6×104 N · s
D.
-5.9 x 104 N · s
E.
-3.4×104 N · s
5. A constant force of 4.5 N acts on a 7.2-kg object for 10.0 s. What is the change in the object's
velocity?
A.
45m/s
B.
3.2 m/s
C.
1.2 m/s
D.
4.33 m/s
E.
6.3 m/s
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II- Solve the following problems
[11 marks]
6. Abdulla’s mass is 43.5 kg, and he is riding his 8.00-kg bicycle. What is the combined
momentum of Abdulla and his bike if they are going 2.40 m/s? (3 marks)
p=mxv
= (43.5 + 8.00) x 2.40
= 123.6kg.m/s
7. A 0.145-kg baseball is moving at 35m/s when it is caught by a player.
a. Find the change in momentum of the ball (3 marks)
∆p = m (vf – vi)
= 0.145 (0-35)
= - 5.1 kg.m/s
b. If the ball is caught with the mitt held in a stationary position so that the ball stops in 0.05s,
what is the average force exerted on the ball? (3 marks)
F∆t
= ∆p
F x 0.05 = -5.1
F
= -102N
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8. A 0.065-kg tennis ball moving to the right with a speed of 15 m/s is struck by a tennis racket,
causing it to move to the left with a speed of 15 m/s. If the ball remains in contact with the
racquet for 0.020 s, what is the magnitude of the average force experienced by the ball?
(3 marks)
F∆t
= m(vf – vi)
F x 0.020 = 0.065 (-15 – 15)
F
= -97.5N
9. A 7.0 kg bowling ball is rolling down the alley with a velocity of 2.0m/s. For the impulse shown
below, find the resulting speed of the bowling ball. (3 marks)
Pi = m x v = 7.0 x 2.0 = 14.0 kg.m/s
I = bxh = 1 x 5 = 5 N.s
F∆t = pf – pi
5 = pf – 14
pf = 19 kg.m/s = m x vf
vf = 19/7 = 2.7m/s
III-Answer the following questions
[5 marks, 2 each]
9. Can a bullet have the same momentum as a truck? Explain. ( 3 marks)
Yes, for a bullet to have the same momentum as a truck, it must have a higher velocity
because the two masses are not the same.
10. A stunt person jumps from the roof of a tall building, but no injury occurs because the person
lands on a large, air-filled bag. Explain why no injury occurs? ( 2 marks)
The bag increases the amount of time during which the momentum is changing, and therefore reduces
the average force on the person.
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T3 Quiz (2)-Momentum and Collisions
Grade/Cluster
Section
Name
ID
Grade 11
11.
Subject
Core Physics
Date
/ /2013
Duration 20 min
Score/20
I- Choose the best answer
[4 marks, 1 each]
During an elastic collision between two balls, which of the following statements is correct?
A.
both momentum and kinetic energy are conserved
B.
Momentum is conserved but kinetic energy is not conserved
C.
momentum is not conserved but kinetic energy is conserved
D.
neither momentum nor kinetic energy is conserved
E.
momentum is sometimes conserved but kinetic energy is always conserved
2. An object, moving at a constant speed, has a momentum p and kinetic energy KE. Which one of
the following combinations is correct if the speed of the object is doubled?
Momentum
Kinetic energy
A.
2p
2KE
B.
2p
4KE
C.
p
2KE
D.
p
4KE
E.
4p
4KE
3. A 2-kg mass moving with a velocity of 7m/s collides elastically with a 4-kg mass moving in the
opposite direction at 4m/s. The 2-kg mass reverses direction after the collision and has a new
velocity of 3m/s. What is the new velocity of the 4-kg mass?
A.
B.
C.
D.
E.
Quiz 3
-1m/s
1m/s
6m/s
4m/s
5m/s
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4. Three identical balls, each with a mass of m, are in contact with each other in a straight line
and at rest on a smooth horizontal surface. Another ball of the same size but having a mass of
2m, move with a constant velocity v and collide elastically in the same straight line with the
three stationary balls.
Which one of the following diagrams represents the situation immediately after the collision?
A.
B.
C.
D.
E.
Both momentum and KE must be conserved
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II- Solve the following problems:
[12 marks]
5. A 0.4-kg mass traveling 3 m/s hits a 0.6-kg mass initially at rest.
a. Find the speed of the 0.4-kg mass if the speed of the 0.6-kg mass after the collision is 2.4 m/s.
(3marks)
m1v1i + m2v2i = m1v1f + m2v2f
0.4 x 3 + 0.6 x 0 = 0.4 x v1f + 0.6 x 2.4
v1f = -0.6m/s
b. Is this an elastic or an inelastic collision? Show how you arrived at your answer (4 marks)
Total KE before collision
Total KE after Collision
1/2 m1v1i 2 + 1/2 m2v2i2
= 1/2 m1v1f2 + 1/2 m2v2f2
=1/2 x 0.4 x 32 + 0
=1/2 x 0.4 x (-0.6)2 + 1/2 x 0.6 x 2.42
= 1.8J
= 1.8J
Since KE before collision = KE after collision, it is an elastic collision ( momentum and KE
conserved)
6. Two carts having masses 1.5kg and 0.7kg, respectively, are initially at rest and held together
by a compressed massless spring. When released, the 1.5kg cart moves to the left with a velocity
of 7m/s. What are the velocity and direction of the 0.7kg cart? ( 3 marks)
(m1 + m2)vi = m1v1f + m2v2f
0 = -1.5 x 7 + 0.7 x v2f
v2f = 15m/s to the right
7. Object #1 moves towards object #2, whose mass is twice that of object #1 and which is
initially at rest. After their impact, the objects lock together and move with what fraction of
object#1’s initial kinetic energy? ( 2 marks)
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KE i
KE f
1/2 m1v1i  1/2 m 2 v 2i
2
m1v1i  m 2 v 2i  (m1  m 2 )vf
mv1i  0  (m  2m)v f
1
vf  v1i
3
 1/2 m1v1i  0
2
 KE i
III- Answer the following questions:
2
1 / 2(m1  m 2 )vf 2
1
 1/2 (m  2m) x( v1i ) 2
3
1 1
 1/2 x 3m x x v1i
3 3
1
2
 1/2 mv 1i x
3
1
 KEi
3
2
[4 marks]
8. State the law of conservation of momentum indicating the conditions required for total
momentum of colliding objects to be conserved.
In a closed, isolated system, the total momentum before collision equals the total momentum
after the collision
9. A spacecraft in outer space increases its velocity by firing its rockets. How can hot gases from
the rocket engine change the velocity of the craft when there is nothing in space for the gases to
push against?
The hot gases and the spacecraft form a closed isolated system, therefore momentum is
conserved.
The change in momentum of the gases in one direction causes a equal change in momentum of
the spacecraft in the opposite direction
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Quiz ( 3) Thermal Energy
Grade/Cluster
G11
Subject
PHYSICS
Section
Date
Name
Duration 20 min
ID
Score/20
I-Choose the best answer.
[7 marks, 1 each]
1. The energy needed to melt 1 kg of a substance is called the------------------.
A. freezing point
B. condensation
C. heat of fusion
D. heat of vaporization
2. The temperature at which all added thermal energy is used to change a liquid to a gas is
the…………………………………
A. boiling point
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B.
melting point
C. heat of vaporization
D. heat of fusion
3. The temperature of absolute zero on a Kelvin scale is equal __________.
A. 00 C
B. 1000 C
C.
– 2730 C
D. 2730 C
4. You feel heat as you approach a fire mostly by way of __________.
A. conduction
B. convection
C. radiation
D. thermal expansion
5. A 0.04 kg sample of liquid mercury at boiling absorbs 10880J to vaporize into a
gas at same
temperature. The heat of vaporization of mercury is _______________.
A. 435 J/Kg
B. 2.72x105 J/Kg
C. 7.2 x105 J/Kg
D. 4180 J/Kg
Use the table below to answer problems 6 and 7.
6. A 9.75-kg block of metal requires 6.14x10 2 kJ of heat to change from a solid to a liquid at
its melting point. What is the metal?
A. gold
B. iron
C. lead
D. silver
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7. How much heat is needed to convert 2 kg sample of liquid methanol into a gas?
A. 5.5 x10 4 J
B. 2.2 x10 5 J
C. 4.4 x10 5 J
D. 1.8 x10 6 J
II- Solve the following problems:
[10 marks]
1. How much heat must be added to a 250 g aluminum pan to raise its temperature from
20°C to 85°C? The specific heat of aluminum is 897 J/kg·K.
( 3 marks )
Q=
m x C x ( tf-ti )
Q = 0.250 x 897 x ( 85 – 20 )
= 14576.25
J
2. How much heat is absorbed by 200 g of ice at (- 85 °C ) to become Water at 0.0°C? Given
that Hf (ice) = 3.34 x 10 5 J/kg and C(ice) = 2060 J/kg.K
( 4 marks )
Q=
mC∆t
+
mHf
=[ 0.200X2060 ( 0 - - 85 ) ]+ [ 0.200x 3.34 x 10 5 ]
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=
35020
=
+
66800
101820 J
3. A foam cup with negligible specific heat is used as a calorimeter. If you mix 175 g of water
at 20.0°C and 125 g of water at 95.0°C, what is the final temperature of the water after it is
mixed? Assume no loss of heat to the air or container.
Q gained
( cold water )
+
Q lost
( hot water )
( 3 marks )
=0
0.175xCx( tf – 20 ) + 0.125x Cx ( tf-95 ) = 0
tf = 51.25 oC
remember : the two objects are water. So, the specific heat ( C ) is the same that can be
canceled.
III- Answer the following questions:
[3 marks; 1.5 each]
1. What is the difference between thermal energy and temperature?
Thermal energy is the total thermal energy of the molecules of the object.
Temperature is the average thermal energy per molecule of the object.
2. Why do easily vaporized liquids, such as acetone and methanol, feel cool to the skin?
As the thermal energy transferred from the hot object ( hand )which lost thermal energy
feeling cool to the cold object ( liquids ) which gained energy evaporating the liquid.
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