Topic 5 - Forces & Motion Flashcards
What is a force?
A force is a push or a pull on an object
Contact Forces
Air resistance (drag)
Friction
Tension
Thrust
Lift
Non-contact forces
Magnetic
Electrostatic
Gravitational
Weak nuclear force
Strong nuclear force
Balanced Forces
- If two forces are balanced, they
have the same magnitude but are
acting in opposite directions. - If two balanced forces are acting
on an object, the object will not
change its motion. - A stationary object will stay still.
- A moving object will continue
moving in the same direction and
at the same speed.
Newton’s 1st Law of Motion - Balanced Forces
An object at rest will remain at rest
unless acted upon by an external and unbalanced force.
An object in motion will remain in motion unless acted upon by an external and unbalanced force
Unbalanced Forces
- When two forces acting on an
object are not equal in size, we
say that they are unbalanced
forces. - Unbalanced forces change the
way something is moving. - They can make objects start to
move, speed up, slow down or
change direction.
Newton’s 2nd Law of Motion - Unbalanced Forces
The rate of change of the momentum of a body is directly proportional to the net force acting on it, and the direction of the change in momentum takes place in the direction of the net force.”
Force = mass × acceleration
Newton’s 3rd Law of Motion - Equal but opposite forces
To every action (force applied) there is an equal but opposite reaction (equal force applied in the opposite direction)
The Normal Force
The normal force is the force that any surface pushes back up↑ with.
The normal force is also referred to as the normal reaction force.
The normal force is given the symbol R
Weight
Weight is the force on an object
due to gravity
W = m × g
g is acceleration due to gravity.
m is mass of the object (kg).
g = 9.81 m s−2 on earth.
g = 0 m s−2 in space.
g = 1.625 m s−2 on the moon.
