Summary Physics 2.1, 2.2, 2.3, 2.4
2.1 Types of Forces
Recognizing forces
- Elastic deformation the object goes back to the original shape after a force being executed on
it.
- Plastic deformation the shape of the object does not go back to the original shape after a
force.
- Forces can push or pull something
- Forces can change the velocity or direction of an object
Types of forces:
1. Muscular strength
2. Resilience springy material
3. Tension in rope
4. Gravity Fgravity = m x g
5. Magnetic
Measuring forces
- You can measure forces using a dynamometer
Fg = m x g
Where:
- Fg is the force of gravity in newtons (N)
- m is the mass in kilograms (kg)
- g is the gravity on the Earth’s surface in newtons per kilogram (N/kg)
Drawing forces
- A force has a magnitude, a direction and a point of application. A variable with these properties
is called a vector.
o The length of the arrow gives the magnitude
o The direction shows the direction of the force
o The starting point of the vector shows where the force is being exerted
Centre of gravity
- Gravity applies on all points on an object.
o But you draw an arrow (vector) from the center of gravity C.
It’s not always in the middle!
, 2.2 More than one force
Two forces in equilibrium
- 2 forces are cancelling each other out
o They are in equilibrium
o The forces are equal and in opposite direction
So nothing happens
- The fruit bowl pushes the table down a little bit
o The tabletop exerts a force upwards on the fruit bow, perpendicular to the tabletop.
This is called normal force Fn
Force and extension
- The extension is the amount that a spring stretches
o It is the number of centimeters that the length of the spring increases in
comparison with the zero position.
- The extension is directly proportional to the force
o Because of this, you always get the same value if you divide the force by the
corresponding extension.
The value C is called the spring constant.
- C = F/x
o C is the spring constant in newtons per meter (N/m)
o F is the force that pulls on the spring in newtons (N)
o x is the extension of the spring in meters (m).
- Spring constants are often given in N/cm, this is more convenient
Determining the resultant
- When forces are in equilibrium the resultant Fres on the object is 0N
o All the forces added up to each other
Adding forces together
- If two forces are acting in different direction you can use the parallelogram method
1. Choose a suitable scale of forces
2. Draw in the two forces at correct scale and correct angles
3. Complete the parallelogram
4. Draw the resultant arrow to the opposite corner
5. Measure the length of the arrow. Use the scale to determine the magnitude
6. Determine the direction of the resultant by measuring the angle
2.1 Types of Forces
Recognizing forces
- Elastic deformation the object goes back to the original shape after a force being executed on
it.
- Plastic deformation the shape of the object does not go back to the original shape after a
force.
- Forces can push or pull something
- Forces can change the velocity or direction of an object
Types of forces:
1. Muscular strength
2. Resilience springy material
3. Tension in rope
4. Gravity Fgravity = m x g
5. Magnetic
Measuring forces
- You can measure forces using a dynamometer
Fg = m x g
Where:
- Fg is the force of gravity in newtons (N)
- m is the mass in kilograms (kg)
- g is the gravity on the Earth’s surface in newtons per kilogram (N/kg)
Drawing forces
- A force has a magnitude, a direction and a point of application. A variable with these properties
is called a vector.
o The length of the arrow gives the magnitude
o The direction shows the direction of the force
o The starting point of the vector shows where the force is being exerted
Centre of gravity
- Gravity applies on all points on an object.
o But you draw an arrow (vector) from the center of gravity C.
It’s not always in the middle!
, 2.2 More than one force
Two forces in equilibrium
- 2 forces are cancelling each other out
o They are in equilibrium
o The forces are equal and in opposite direction
So nothing happens
- The fruit bowl pushes the table down a little bit
o The tabletop exerts a force upwards on the fruit bow, perpendicular to the tabletop.
This is called normal force Fn
Force and extension
- The extension is the amount that a spring stretches
o It is the number of centimeters that the length of the spring increases in
comparison with the zero position.
- The extension is directly proportional to the force
o Because of this, you always get the same value if you divide the force by the
corresponding extension.
The value C is called the spring constant.
- C = F/x
o C is the spring constant in newtons per meter (N/m)
o F is the force that pulls on the spring in newtons (N)
o x is the extension of the spring in meters (m).
- Spring constants are often given in N/cm, this is more convenient
Determining the resultant
- When forces are in equilibrium the resultant Fres on the object is 0N
o All the forces added up to each other
Adding forces together
- If two forces are acting in different direction you can use the parallelogram method
1. Choose a suitable scale of forces
2. Draw in the two forces at correct scale and correct angles
3. Complete the parallelogram
4. Draw the resultant arrow to the opposite corner
5. Measure the length of the arrow. Use the scale to determine the magnitude
6. Determine the direction of the resultant by measuring the angle
