Activity Sheet – Newtonian Laws of Motion
Name: Xyreen Yzabel Lacson
Grade: 8 – Gardner
Isaac Newton’s three laws of motion are three physical laws that, together, laid the
foundation for classical mechanics. They describe the relationship between a body and the forces
acting upon it, and its motion in response to those forces.
First Law of Motion or Law of Inertia
It states that every object will remain at rest or in uniform motion in a straight line unless
compelled to change its state by the action of an external force.
Inertia is also defined as the tendency of object to resist changes to its state of motion.
RELATIONSHIP OF MASS AND INERTIA:
Greater mass = Greater inertia
Lesser mass = Lesser inertia
Example: You experience a jolt when the elevator suddenly starts.
Video:
https://www.youtube.com/watch?v=YbWjx3LUc0U
https://www.youtube.com/watch?v=qq1Whusk8No
Questions:
1. A ball is on the floor. You tried to kick it and it moved. After some time of hitting the wall, it finally
stopped. In this given scenario, underline the inertia at rest, ONCE and the inertia in motion TWICE.
2. Why do you think the ball continuously moves before it hit the wall?
3. You are seated on a swivel chair and somebody pulled it suddenly. What will be your body’s initial
reaction (what is the direction of the body’s movement when pulled?)? Draw an arrow on the second
diagram (after) to show what will be body’s direction of movement as it was pulled.
Direction of the
sudden pulling force
Before: Body’s original position After: Body’s position when pulled.
when not yet pulled.
4. In the coin and egg drop experiment, what is the direction of the force (the sudden flick of the
cardboard) and the direction of the egg and coin? (Please refer to this link:
https://www.sciencefun.org/kidszone/experiments/egg-drop/)
Second Law of Motion or Law of Acceleration
It states that acceleration (change in speed) happens when a force act on a certain mass (object).
It can be mathematically represented as: F = m*a
Relationship of FORCE and ACCELERATION:
Lesser force = Lesser acceleration
Greater force = Greater acceleration
Relationship of MASS and ACCELERATION:
Lesser mass = Greater acceleration
Greater mass = Greater acceleration
Example: Pedaling a bicycle. Your bicycle is the mass. Your leg muscles pushing on the pedals of
your bicycle is the force. When you push on the pedals, your bicycle accelerates. You are
increasing the speed of the bicycle by applying force to the pedals.
Video:
https://www.youtube.com/watch?v=nO7XeYPi2FU
Questions:
1. You pushed an object with a little amount of force and it moved a little. What do you need to do to move
the object farther?
2. In which are you going to move faster when you apply the same amount of force? Moving a chair alone
or moving a chair with 10 books?
3. Between a cart and a car, which of these two needs to be applied with greater amount of force to
move? Why?
Refer to the Techan’s Triangle below and solve the following equations. Use GRESA method
GRESA METHOD
Given
Required (what is asked in the problem)
Equation (the formula to be used)
Solution
Answer (always box the final answer)
FORMULA REFERENCE:
Where:
F = force --- unit: Newton (N)
M = mass --- unit: kilogram (kg)
A = acceleration --- unit: meters per second squared (m/s2)
And don’t forget to attach the unit in your final answer! 😊
Problem 1: If a 5 kg ball is accelerating 3 m/s 2, what is the amount of force on it? (List down the givens using
the GRESA method.)
Given:
m = 5 kg
a = 2 m/s2
Required: Force (F)?
Equation: F = m*a
Solution: F = 5 * 2
Answer: 15 N
Problem 2: A person on a scooter is accelerating 2 m/s 2. If the person has a mass of 50 kg, how much force is
acting on that person?
Problem 3: An object with a force of 33 N on it is accelerating at 15m/s2. What is the mass of the object?
Problem 4: An object with a mass of 13kg experiences a force of 7 N. What is the acceleration of the object?
Problem 5: A batter hits a baseball with 500 N and the ball is accelerated at 25 m/s 2. What is the mass of the
ball?
Third Law of Motion or Law of Interaction
It states that for every action (force) in nature there is an equal and opposite reaction.
Example: Example: The gas that come out from the rocket apply a huge force on the ground (action). The
ground applies an equal and opposite force (reaction) and helps the rocket move upward.
Video:
https://www.youtube.com/watch?v=TVAxASr0iUY
Directions: Answer the following questions.
1. Why don’t we sink on the ground when we walk? (How is the Law of
Interaction applied in the given situation?
2. Draw and label the arrows on the image below to show the action-reaction forces. What is the action force?
What is the reaction force? Write your answers beside each arrows.
3. Draw other examples showing the application of the Law of Interaction.
Example 1 Example 2
Example 3
