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Forces
• Remember a force is a push (or pull)
Forces
• Force is measured in Newtons
Forces
• There are many types of forces;
electrostatic, magnetic, upthrust, friction,
gravitational………
Scalars and Vectors
No direction
vectors
scalars
Magnitude (size)
temperature
mass
Magnitude and direction
velocity
force
speed
acceleration
Representing vectors
Vectors can be represented by arrows.
The length of the arrow indicates the
magnitude, and the direction the direction!
Copy please!
Adding vectors
For example;
Resultant force
6N
4N
2N
Robert Hooke
Investigating forces and springs
You are going to investigate how much a spring stretches when a force is
applied to it.
The amount a spring stretches is called its extension. This is the
difference in length between the stretched spring and the length of the
spring when it was unstretched.
(Remember we are looking at the force on the spring. A mass of 100g will
have a weight (force of gravity pulling it down) of 1 Newton.
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Add masses to your spring and carefully measure its extension. You can
do this until the spring breaks! (but you must wear goggles and be careful
during this investigation).
Your experimental report will include the following
A table of results
A graph of your results
A conclusion describing what you have discovered (think about this!)
Table of results
Force (N)
0
Length of spring Extension (cm)
(cm)
3.4
0
1
5.4
2.0
2
7.4
4.0
3
9.4
6.0
Graph
Force (N)
Extension (cm)
Go!
Hooke’s law (F = kx)
Limit of proportionality
Force
(N)
The extension of a spring is proportional to
the force applied (until the limit of
proportionality is reached). The gradient
of the graph is equal to k, the spring
constant.
Extension (x) (cm)
Steel, glass and wood!
Force
Even though they don’t
stretch much, they obey
Hooke’s law for the first part
of the graph
Extention
Rubber
Force
Extension