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PHYSICS ANSWERSHEET
Critical Thinking Questions Part 1
1. Newton’s First Law is associated with Inertia.
2. The acceleration increases as you increase the force on an object.
3. The acceleration increases on less massive object.
4. Newton’s Second Law is dependent on the mass and acceleration of an object.
5. Force causes an object to slowdown or speed up.
6. 3
rd
Law is known as the Law of action-reaction.
7. Third Law of Interaction Law.
8. The acceleration will also be doubled after the force was doubled.
9. The acceleration will decrease if the mass was doubled.
10. 1N = 1kg m/s
2
Exercises
1. On this situation, her for purse has fallen on the ground because of the sudden stop of the vehicle.
2. Newton’s Third Law of Motion is present on the situation as the diver jumps on the board it shows the
action is other words the force exerted by the diver was the action. On the other hand, as the diver
jumps there will be the force from the board that pushes the diver upwards causing him to fly and that
thing was the reaction.
3. The Newton’s Second Law of Motion
4. There will be 3 N of force in 3kg m/sec
2
since the equivalent of 1N is 1kg m/s
2
.
5. The cart is required to have 19.5 N for it to accelerate at 0.3 m/sec
2
.
6. a =
a =


a = 0.2 m/s
2
The acceleration of the wagon is 0.2 m/s
2
.
7. The 3 pairs of action reaction forces present in the situation
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- The force exerted by the ball to the ground
- The force exerted by the hand of the player to the ball
- The force exerted by the man’s foot to the ground.
Critical Thinking Questions Part II
1. The acceleration of an object is the result of unbalanced forces.
2. If the forces are balanced then there will be no resulting acceleration.
3. The object's resistance to change in motion is solely dependent on the mass of the object.
4. Inertia is solely dependent on the mass of the object
5. Force is required to cause acceleration.
6. The net force of the cart when pushed 5N on its opposite side, is zero (0).
7. The net force of the cart is still zero (0).
Exercises
1. According to Newtons first law, the rock will continue in motion in the same direction at constant
speed
2. Yes, even in space objects have mass. And if they have mass, they have inertia. That is, an object in
space resists changes in its state of motion. A force must be applied to set a stationary object in motion
3. The ball doesn’t roll on forever because of the frictional force present on the ground.
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4. 0N, an object in motion will maintain its state of motion. The presence of an unbalanced force
changes the velocity of the object.
5. As the bull moose will also do the zigzag move chasing Ben, it would be its disadvantage as Law of
Inertia depends solely on mass. The more mass you have the more inertia you have, which it can make
the bull moose hard to change its state of motion.
6.
a) Graph B best describes the motion of the object since it is stated that the ball does have the airtime
that made its acceleration to increase, as the ball enter the water surface of the pool, it is supposed that
equal amount of force is resisting upwards, so the ball would have a balanced force that made it
constant on its net force.
b) False. When the forces are balanced, the object will not change its motion from that point forward.
This does not mean that the object will stop moving but rather that it will continue to move at the
velocity that it was moving at when it hit the water.
Critical Thinking Questions Part III
1. Acceleration is dependent on the net force and the mass of the object. Acceleration is directly related
to force (if force increases, acceleration must also increase, and vice versa). Acceleration is inverted
related to mass (if mass increases, acceleration must decrease).
2. If an object is not accelerating, that means that the net force on the object is 0.
3. The acceleration will also be negative if the net force on the object is in the negative direction.
4. If the net force is doubled, the acceleration is also doubled.
5. If the net force is unchanged and the mass is doubled, the acceleration must be halved.
6. F = m x a = (2569.6 kg) x (4.65 m/s
2
) = 11,948.64 N
7.
a) When the bowling ball is at rest, the net force acting on the ball is 0 N.
b) There is a -2.3 N frictional force opposing the force that is applied to the ball. The net force is 22.8 N -
2.3 N = 20.5 N since the forces are acting in opposite directions. (Since there are no specific directions
given in the problem, we can’t include a direction for net force)
c) F = m x a -> a = F/m = 20.5 N/7.26 kg = 2.8 m/s
2
d) The ball is rolling at a constant speed so there is no acceleration. Since there is no acceleration, there
is no net force (0 N) acting on the ball.
e) t = V
f
/ a V
1
= 0 a = 2.8 m/s
2
V
f
= 4.2 m/s
2
t = t = 4.2 m/s
2
/ 2.8 m/s
2
t = 1.5 m/s
2
Exercises
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8)
Net Force (N)
Mass (kg)
Acceleration
5.0
2.5
2.0 m/s
2
2.32
12
0.19 m/s
2
18.2
1.967
9.25 m/s
2
0.87
21.2
0.04 m/s
2
180
1.793
100.39 m/s
2
9)
Net Force (N)
Mass (kg)
Acceleration
16
4.0
4.0 m/s
2
25.0
5.0 kg
4.998
53
3
17.67 m/s
2
172.44
36.96 kg
4.665
4201.75 N
1.225
3.43
10) m=2000kg F=4200N a=


= 2.1m/s²
11) F = ma 25 N = (0.30 kg) a a = 26 N/ 0.30 kg a = 83.33 m/s
2
12) F = ma m = 68 kg a = 1.2 m/s
2
F = (68 kg) (1.2 m/s
2
) F = 81.6 kg m/s
2
13) F = ma m = F/a F = 30 N a = 5 m/s
2
m=


= 6 kg
14) F = ma m = 1000 kg a = 9.8 m/s
2
F = (1000 kg) (9.8 m/s
2
) F = 9800 kg m/s
2
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15) F = ma m = F/a F = 4500 N a = 5 m/s
2
m=


= 900 kg
16) F = ma a = F/m a=


= 1.875 m/s
2
17) F = 6600 N v = 107 m/s t = 2.3 secs a =?
a =


= 46. 5 m/s
2
F = ma m = f/a m =


m = 141.93 kg
Critical Thinking Questions Part IV
1. All forces result because of interaction between objects.
2. Forces come in pairs called Action-reaction forces.
3.
4.
a) The physics student exerts 500 N on the towards left
b) The wall exerts 500 N on the rope towards right
c) There is no force, or the force is 0 since they have balanced forces.
d) No, the physics student doesn’t move nor accelerate.
e) The physics student will accelerate backwards.
f) He would be pulled toward the wall since there is less friction on the ice he is standing at.
g) It is called the Normal Force.
5.
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6.
a) The action force is the rocket push on gas
b) The reaction is the gas on the rocket
c) Rocket is its own system, so gas creates outside force on the rocket
7.
a) Fb = 5 (10) = 50 N
b) The man exerts 50 N upwards
c) 375 N + 50 N = 425 N upwards
d)

= 212.5 N
8. They have the same forces. As the Newton’s Third law stated that to every action there is always an
equal and opposite reaction.
9. B. The force on the rifle equals the force on the bullet. Acceleration depends on both force and mass.
The bullet has a greater acceleration since it has a smaller mass compared to the recoiling rifle.
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PHYSICS ANSWERSHEET Critical Thinking Questions – Part 1 1. Newton’s First Law is associated with Inertia. 2. The acceleration increases as you increase the force on an object. 3. The acceleration increases on less massive object. 4. Newton’s Second Law is dependent on the mass and acceleration of an object. 5. Force causes an object to slowdown or speed up. 6. 3rd Law is known as the Law of action-reaction. 7. Third Law of Interaction Law. 8. The acceleration will also be doubled after the force was doubled. 9. The acceleration will decrease if the mass was doubled. 10. 1N = 1kg m/s2 Exercises 1. On this situation, her for purse has fallen on the ground because of the sudden stop of the vehicle. 2. Newton’s Third Law of Motion is present on the situation as the diver jumps on the board it shows the action is other words the force exerted by the diver was the action. On the other hand, as the diver jumps there will be the force from the board that pushes the diver upwards causing him to fly and that thing was the reaction. 3. The Newton’s Second Law of Motion 4. There will be 3 N of force in 3kg m/sec2 since the equivalent of 1N is 1kg m/s2. 5. The cart is required to have 19.5 N for it to accelerate at 0.3 m/sec2. 6. a = a= 𝑓 𝑚 2 𝑘𝑔 𝑚/𝑠2 10 𝑘𝑔 a = 0.2 m/s2 The acceleration of the wagon is 0.2 m/s2. 7. The 3 pairs of action – reaction forces present in the situation - The force exerted by the ball to the ground - The force exerted by the hand of the player to the ball - The force exerted by the man’s foot to the ground. Critical Thinking Questions – Part II 1. The acceleration of an object is the result of unbalanced forces. 2. If the forces are balanced then there will be no resulting acceleration. 3. The object's resistance to change in motion is solely dependent on the mass of the object. 4. Inertia is solely dependent on the mass of the object 5. Force is required to cause acceleration. 6. The net force of the cart when pushed 5N on its opposite side, is zero (0). 7. The net force of the cart is still zero (0). Exercises 1. According to Newtons first law, the rock will continue in motion in the same direction at constant speed 2. Yes, even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion 3. The ball doesn’t roll on forever because of the frictional force present on the ground. 4. 0N, an object in motion will maintain its state of motion. The presence of an unbalanced force changes the velocity of the object. 5. As the bull moose will also do the zigzag move chasing Ben, it would be its disadvantage as Law of Inertia depends solely on mass. The more mass you have the more inertia you have, which it can make the bull moose hard to change its state of motion. 6. a) Graph B best describes the motion of the object since it is stated that the ball does have the airtime that made its acceleration to increase, as the ball enter the water surface of the pool, it is supposed that equal amount of force is resisting upwards, so the ball would have a balanced force that made it constant on its net force. b) False. When the forces are balanced, the object will not change its motion from that point forward. This does not mean that the object will stop moving but rather that it will continue to move at the velocity that it was moving at when it hit the water. Critical Thinking Questions – Part III 1. Acceleration is dependent on the net force and the mass of the object. Acceleration is directly related to force (if force increases, acceleration must also increase, and vice versa). Acceleration is inverted related to mass (if mass increases, acceleration must decrease). 2. If an object is not accelerating, that means that the net force on the object is 0. 3. The acceleration will also be negative if the net force on the object is in the negative direction. 4. If the net force is doubled, the acceleration is also doubled. 5. If the net force is unchanged and the mass is doubled, the acceleration must be halved. 6. F = m x a = (2569.6 kg) x (4.65 m/s2) = 11,948.64 N 7. a) When the bowling ball is at rest, the net force acting on the ball is 0 N. b) There is a -2.3 N frictional force opposing the force that is applied to the ball. The net force is 22.8 N 2.3 N = 20.5 N since the forces are acting in opposite directions. (Since there are no specific directions given in the problem, we can’t include a direction for net force) c) F = m x a -> a = F/m = 20.5 N/7.26 kg = 2.8 m/s2 d) The ball is rolling at a constant speed so there is no acceleration. Since there is no acceleration, there is no net force (0 N) acting on the ball. e) t = Vf / a V1 = 0 a = 2.8 m/s2 Vf = 4.2 m/s2 t = t = 4.2 m/s2 / 2.8 m/s2 t = 1.5 m/s2 Exercises 8) Net Force (N) Mass (kg) Acceleration 5.0 2.5 2.0 m/s2 2.32 12 0.19 m/s2 18.2 1.967 9.25 m/s2 0.87 21.2 0.04 m/s2 180 1.793 100.39 m/s2 Net Force (N) Mass (kg) Acceleration 16 4.0 4.0 m/s2 25.0 5.0 kg 4.998 53 3 17.67 m/s2 172.44 36.96 kg 4.665 4201.75 N 1.225 3.43 9) 10) m=2000kg F=4200N a= 4200 𝑘𝑔 𝑚/𝑠2 2000 𝑘𝑔 = 2.1m/s² 11) F = ma 25 N = (0.30 kg) a a = 26 N/ 0.30 kg a = 83.33 m/s2 12) F = ma m = 68 kg a = 1.2 m/s2 F = (68 kg) (1.2 m/s2) F = 81.6 kg m/s2 13) F = ma m = F/a F = 30 N a = 5 m/s2 m= 30 𝑘𝑔 𝑚/𝑠2 5 𝑚/𝑠2 = 6 kg 14) F = ma m = 1000 kg a = 9.8 m/s2 F = (1000 kg) (9.8 m/s2) F = 9800 kg m/s2 15) F = ma m = F/a F = 4500 N a = 5 m/s2 m= 16) F = ma a = F/m a= 12 𝑘𝑔 𝑚/𝑠2 6.4 𝑘𝑔 4500 𝑘𝑔 𝑚/𝑠2 5 𝑚/𝑠2 = 900 kg = 1.875 m/s2 17) F = 6600 N v = 107 m/s t = 2.3 secs a =? a= 107 𝑚/𝑠 2.3 𝑠 = 46. 5 m/s2 F = ma m = f/a m = 6600 𝑘𝑔 𝑚/𝑠2 46.5 𝑚/𝑠2 m = 141.93 kg Critical Thinking Questions – Part IV 1. All forces result because of interaction between objects. 2. Forces come in pairs called Action-reaction forces. 3. 4. a) The physics student exerts 500 N on the towards left b) The wall exerts 500 N on the rope towards right c) There is no force, or the force is 0 since they have balanced forces. d) No, the physics student doesn’t move nor accelerate. e) The physics student will accelerate backwards. f) He would be pulled toward the wall since there is less friction on the ice he is standing at. g) It is called the Normal Force. 5. 6. a) The action force is the rocket push on gas b) The reaction is the gas on the rocket c) Rocket is its own system, so gas creates outside force on the rocket 7. a) Fb = 5 (10) = 50 N b) The man exerts 50 N upwards c) 375 N + 50 N = 425 N upwards d) 425 𝑁 2 = 212.5 N 8. They have the same forces. As the Newton’s Third law stated that to every action there is always an equal and opposite reaction. 9. B. The force on the rifle equals the force on the bullet. Acceleration depends on both force and mass. The bullet has a greater acceleration since it has a smaller mass compared to the recoiling rifle. Name: Description: ...
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