Forces and Pressure
A force is a/can
push or pull
make an object move
stop an object
speed up an object
slow down an object
change direction of an object
SI unit: Newton(N)
Type of forces
Contact force: The push experienced when two objects are pressed together.
Weight: The gravitational pull of the Earth on an object.
Friction: The force that opposes motion and it exists between the surfaces of two objects in contact.
Tension: The pull at the both ends of a stretched spring, string or rope.
Resistance: This force is also known as viscous force where it is found in fluids such as air and water.
Electric Force: The push or pull between electric charges.
Magnetic Force: The push or pull between magnets or magnets on magnetic materials.
Vector quantities
Vector quantities are physical quantities that have both magnitude and direction
Vector quantities include velocity, acceleration and forces.
Resultant force
=net force
Answer format:
Resultant force = _
= N, which acts towards the left/right
Effect of forces
When the forces acting on a body is unbalanced, the net force can cause a
- Stationary object to start moving
- A moving object to increase/decrease its speed/change its direction
Parallelogram Method
Use an appropriate scale (Eg: 1 cm :1 N)
Step 1: Draw both vectors starting from the same origin.
Step 2: Complete the parallelogram.
Step 3: The resultant vector is represented by the diagonal of the parallelogram.
Give both magnitude and direction (using bearing) of resultant vector.
Answer Format:
The resultant force has a magnitude of _ N, and acts at an angle of _ degree to the horizontal/verticale
Newton’s 1st Law of motion
An object will remain at rest or move with constant velocity, unless it is acted upon by a net or resultant force.
Balanced Forces
No net or resultant force on an object does not mean no force is acting on the object.
Resultant force is 0 = constant velocity & force is balanced
Newton’s 2nd Law of motion
The net force acting on a body, is the product of mass and acceleration of the same body. The direction of the force is the same as that of the body's acceleration.
Unbalanced force
Will cause a body to
Accelerate/Deccelerate/Change direction
Newton’s 3rd Law of motion
For every action force, there will be an equal and opposite reaction force.
4 characteristics of forces:
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Forces always occur in pairs. Each pair is made of an action and a reaction.
Action and reaction are equal in magnitude.
Action and reaction act in opposite directions.
Action and reaction act on different bodies.
F=ma (Force=mass x acceleration)