Newton’s First Law
What is inertia?
The tendency of an object to resist changes in its motion.
What does Newton’s Second Law state?
Force equals mass times acceleration (F=ma).
What does Newton’s Third Law state?
For every action, there is an equal and opposite reaction.
What is Hooke’s Law?
The force needed to stretch a spring is directly proportional to its extension (F=k.e)
Force measured in Newtons. What is a Newton?
A unit created by Newton. N= kg.m/s2
Give an example of inertia in daily life.
A passenger moving forward when a car suddenly stops (others examples accepted).
If mass increases but force remains the same, what happens to acceleration?
Acceleration decreases.
Give an example of an action-reaction pair.
A swimmer pushes water backward (action), and the water pushes them forward (reaction).
What does the equation F=k.e mean?
Force (F) equals the spring constant (k) times the extension (e).
What is the formula for speed?
Speed = Distance / Time
s=d/t
Why do seatbelts relate to inertia?
They stop a passenger from continuing forward when a car stops.
A car has a force of 200N and a mass of 50kg. Find its acceleration.
a= F/m = 200/50 = 4 m/s2
How does a rocket launch demonstrate this law?
The rocket pushes gases downward (action), and the gases push the rocket upward (reaction).
What are the units for: F, k and e?
F-> Newtons (N)
k-> N/m
e-> meters (m)
If a car travels 78 km in 32 minutes, what is its speed?
s=d/t
s=78/32 =2.44 km/min
s=2.44 x 60 (minutes)= 146.4 km/h
What happens when a tablecloth is pulled quickly under dishes?
The dishes stay in place due to inertia.
How does this law apply to sports?
In soccer, a stronger kick (more force) makes the ball accelerate faster.
If you push against a wall, why don’t you move backward?
The wall pushes back with the same force, but it is too massive to move.
What happens when a spring is stretched beyond its elastic limit?
It does not return to its original shape and may break.
What happens when unbalanced forces act on an object?
The object accelerates in the direction of the net force.
How does mass affect inertia?
The greater the mass, the greater the inertia (more resistance to motion change).
Explain how air resistance affects a falling object.
It slows the object down and opposes gravity, reducing acceleration.
Why do birds need to push air downward to fly?
The downward force on air (action) generates an upward force (reaction) that lifts them.
If a spring has a constant of 100 N/m and is stretched by 0.2m, what is the force?
F=k.e
F=100 x 0.2
F=20 N
A beam is balanced on a pivot at its midpoint.
At what distance from the pivot should the 350 N force be applied to keep the beam balanced?
Mleft=Fleft. dleft
= 180 x 2 = 360 N
Mright=Mleft
Mright=360 N
360=350 x d
360/350= d
d=1.03 m