Physics, a core science subject, plays a significant role in the University of the Philippines College Admission Test (UPCAT). Understanding its fundamental principles is crucial for aspiring students. This overview delves into key components of physics relevant to the UPCAT, specifically the Laws of Motion, Friction, and Work, Energy, and Power.
Laws of Motion
Isaac Newton's Laws of Motion are foundational to understanding the behavior of objects in motion. These laws are critical in analyzing and predicting the motion of objects, a frequent topic in the UPCAT.
1. First Law (Law of Inertia): This law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by a net external force. It highlights the concept of inertia, the tendency of objects to resist changes in their state of motion. Understanding this law helps in analyzing scenarios where forces are balanced or unbalanced.2. Second Law (Law of Acceleration): This law establishes the relationship between force, mass, and acceleration. It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma). This principle is crucial for solving problems involving forces and motion, such as calculating the acceleration of an object given the forces acting upon it.
3. Third Law (Action and Reaction): This law asserts that for every action, there is an equal and opposite reaction. It explains the mutual interactions between objects, such as the propulsion of a rocket or the recoil of a gun. Understanding this law is essential for analyzing interactions between multiple objects.
Friction
Friction is the resistive force that opposes the relative motion of two surfaces in contact. It plays a crucial role in everyday life and various physical phenomena. There are two primary types of friction:
- Static Friction: The force that must be overcome to start the motion of an object at rest. It is generally higher than kinetic friction.
- Kinetic Friction: The force that opposes the motion of an object already in motion.
Understanding friction is essential for solving problems related to the motion of objects on different surfaces, such as calculating the force required to move an object or the deceleration caused by friction.
Work, Energy, and Power
These concepts are interconnected and fundamental to understanding physical processes.
Work: Defined as the product of the force applied to an object and the displacement in the direction of the force (W = Fd). Work is a measure of energy transfer and is crucial for solving problems involving forces and movement.Energy: The capacity to do work. There are various forms of energy, including kinetic energy (energy of motion), potential energy (stored energy), and mechanical energy (sum of kinetic and potential energy). The principle of conservation of energy, which states that energy cannot be created or destroyed, only transformed, is vital for solving physics problems.
Power: The rate at which work is done or energy is transferred (P = W/t). It measures how quickly energy is being used or transferred. Understanding power is crucial for analyzing systems where energy efficiency and rates of work are important, such as in engines and electrical appliances.
UPCAT Examination Reviewer for Physics
Welcome to our UPCAT Reviewer! In this session, you'll have the opportunity to test your understanding of key concepts in Laws of Motion, Friction and Work, Energy and Power. The quiz consists of multiple-choice questions covering various topics. Pay close attention to each question and select the best answer. After completing the exam, check the video below for the answer key and explanations.
LAW OF MOTION
1. Which of Newton's laws of motion explains why a person not wearing a seatbelt flies forward when a car suddenly stops?
A. First Law
B. Second Law
C. Third Law
D. Law of Universal Gravitation
2. What is the formula that represents Newton's Second Law of Motion?
A. F = ma
B. F = mv
C. F = mg
D. F = v/t
3. According to Newton's Third Law of Motion, for every action, there is:
A. An equal and opposite reaction.
B. A greater reaction.
C. A smaller reaction.
D. No reaction.
4. A 10 kg object is pushed with a force of 50 N. What is its acceleration?
A. 2 m/s²
B. 5 m/s²
C. 10 m/s²
D. 50 m/s²
5. Which of the following best illustrates Newton's Third Law of Motion?
A. A car accelerating when the gas pedal is pressed.
B. A book resting on a table.
C. A rocket launching upwards as it expels gas downwards.
D. An apple falling from a tree.
6. What force is needed to accelerate a 20 kg object at 3 m/s²?
A. 60 N
B. 20 N
C. 6.67 N
D. 40 N
7. An object is at rest on a table. According to Newton's First Law, which of the following must be true?
A. There are no forces acting on the object.
B. The forces acting on the object are balanced.
C. The object has zero mass.
D. The object is weightless.
8. If an object is moving at a constant velocity, what can be inferred about the net force acting on it?
A. The net force is positive.
B. The net force is negative.
C. The net force is zero.
D. The net force is increasing.
9. A 5 kg object is acted upon by two forces: 20 N to the right and 10 N to the left. What is the acceleration of the object?
A. 2 m/s² to the right
B. 4 m/s² to the right
C. 6 m/s² to the right
D. 2 m/s² to the left
10. Which of the following scenarios is an example of Newton's First Law of Motion?
A. A car accelerating when the gas pedal is pressed.
B. A ball rolling on the ground eventually coming to a stop due to friction.
C. A rocket launching due to expulsion of gas.
D. A person jumping off a diving board.
FRICTION AND WORK
1. What is the force of friction acting on a 10 kg object that is moving at a constant velocity on a horizontal surface if the coefficient of kinetic friction is 0.4?
A. 4 N
B. 40 N
C. 100 N
D. 400 N
2. Which of the following factors does NOT affect the force of friction between two surfaces?
A. The nature of the surfaces in contact
B. The normal force between the surfaces
C. The area of contact between the surfaces
D. The coefficient of friction
3. A 5 kg block is pushed across a floor with a force of 20 N. If the coefficient of kinetic friction between the block and the floor is 0.3, what is the acceleration of the block?
A. 1 m/s²
B. 2 m/s²
C. 3 m/s²
D. 4 m/s²
4. What is the work done by a force of 10 N moving an object 5 meters along the direction of the force?
A. 2 J
B. 10 J
C. 50 J
D. 100 J
5. If an object is moved in a circular path with constant speed, what can be said about the work done by the centripetal force?
A. Positive work is done
B. Negative work is done
C. No work is done
D. Variable work is done
6. A 2 kg object is lifted vertically by 3 meters. How much work is done against gravity?
(Use g = 9.8m/s2)
A. 19.6 J
B. 29.4 J
C. 58.8 J
D. 78.4 J
7. If the work done to move a 10 kg object 4 meters is 200 J, what is the average force exerted on the object in the direction of motion?
A. 10 N
B. 20 N
C. 30 N
D. 50 N
8. An object slides down a frictionless inclined plane. What can be said about the work done by gravity?
A. It is positive
B. It is negative
C. It is zero
D. It varies
9. A force of 30 N is applied to push a 5 kg box at a constant speed across a horizontal floor. If the coefficient of kinetic friction is 0.5, what is the work done by the applied force over a distance of 4 meters?
A. 30 J
B. 60 J
C. 120 J
D. 150 J
10. A box is pushed up a 30° incline with a constant velocity. If the coefficient of kinetic friction between the box and the incline is 0.4 and the box's weight is 100 N, what is the work done by the applied force to move the box 5 meters up the incline?
A. 300 J
B. 400 J
C. 500 J
D. 600 J
ENERGY AND POWER
1. What is the kinetic energy of a 10 kg object moving with a velocity of 5 m/s?
A. 25 J
B. 50 J
C. 125 J
D. 250 J
2. What is the potential energy of a 5 kg object located 10 meters above the ground? (Use g=9.8m/s2)
A. 49 J
B. 98 J
C. 245 J
D. 490 J
3. A 50 W light bulb is left on for 2 hours. How much energy does it consume?
A. 100 J
B. 360 J
C. 3,600 J
D. 360,000 J
4. What is the power output of an engine that does 5000 J of work in 10 seconds?
A. 50 W
B. 500 W
C. 5,000 W
D. 50,000 W
5. An object with a mass of 3 kg is lifted to a height of 4 meters in 2 seconds. What is the power required to lift the object? (Use g=9.8m/s2)
A. 29.4 W
B. 58.8 W
C. 117.6 W
D. 196.0 W
6. A 60 W motor lifts a 10 kg mass. If the mass is raised to a height of 5 meters, how long will it take? (Use g=9.8m/s2)
A. 5 s
B. 8.17 s
C. 12.5 s
D. 16.3 s
7. A machine does 200 J of work in 4 seconds. What is its power output?
A. 50 W
B. 100 W
C. 150 W
D. 200 W
8. How much work is done by a 100 N force moving an object 3 meters in the direction of the force?
A. 33 J
B. 100 J
C. 300 J
D. 1000 J
9. A car engine has a power output of 80 kW. If the car travels for 2 hours, how much energy is used?
A. 80 kJ
B. 160 kJ
C. 576 kJ
D. 576 MJ
10. If a 75 kg person climbs a 10 meter ladder in 15 seconds, what is the power expended by the person? (Use g=9.8m/s2)
A. 49 W
B. 98 W
C. 490 W
D. 735 W
WATCH THE VIDEO FOR THE ANSWER KEY AND EXPLANATION
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