Warm up
Vocabulary: Force= mass x acceleration
Circle one.
1. An object with More/less mass will have a greater
gravitational pull on other objects.
2. An object that is closer to/ further from a second object
will have a greater gravitational pull.
3. Generally will More/Less force be needed to pull or
push an object?
4. Will pushing an object with More/ Less force cause it to
have a greater acceleration (change in speed)?
Objective
•SWBAT answer questions
IOT explain Newton’s first
and second laws of motion
1st Law of Newton
• Newton’s 1st law of motion= an object at rest will
remain at rest, and an object moving at a constant
velocity will continue moving at a constant velocity,
unless it is acted on by an unbalanced force.
• i. Example: A tennis racket stopping a ball. Gravity and friction are
unbalanced forces that changes an object’s motion.
• ii. Example: Real life: when the alarm clock rings, do you immediately
jump up and get ready for school? Usually, no. You were initially at rest
and you want to stay at rest. This is an example of inertia.
• Iii. Inertia= the tendency of an object to resist a change in motion. The
greater the mass of an object, the greater its inertia, and the greater
the force required to change its motion.
2nd Law of Motion
• A. Newton’s 2nd law of motion= acceleration depends on
the object’s mass and on the net force acting on the
object.
• B. Acceleration= Net force/mass a=Fnet/m.
• Acceleration is measured in m/s2 and mass is measured
in kg.
• C. In other words: Newton’s 2nd law of motion = the net
force acting on an object depends on the object’s mass
and acceleration.
• i. Force= mass x acceleration F=ma. Mass is measured in kg
and acceleration is measured in m/s2. The units for force can be
in Newtons(N) or kg*m/s2.
Sample Problem
• A speedboat pulls a 55-kg water skier. The force causes the
skier to accelerate at 2.0 m/s2. calculate the net force that
causes this acceleration.
• i. Step 1: Identify the needed information! In the equation
F=ma, you need mass and acceleration. Can you find them in
the problem?
Steps to solving
• Mass (m)= 55 kg
• Acceleration (a)= 2.0m/s2
• ii. Step 2: “Plug in” the numbers to the equation F=
(55kg)(2.0m/s2)
• Iii. Step 3: Solve the problem and check your work!
F=110kg*m/s2 or 110 N
Demonstrations
• Watch the different demos in order to understand Newton’s
laws.
• Chair
• Bucket
Evaluation
• Complete guided worksheet #1-10 in your classwork section
of your binder.
Exit Slip
• 1. Objects at rest will stay ____________.
• 2. How would you describe the law of inertia?
• 3. According to Newton’s second law, if you increase the mass
of an object, you will also need to Increase/decrease (circle
one) the force you use to move it.
• Force= ______________x ______________