NEWTON'S LAW OF MOTION
by Abby G
1. Vicosity
1.1. This is the force that opposes motion between layers of fluid.
1.2. Terminal velocity is defined as the constant velocity attained by a body falling in a fluid when the sum of upward forces is equal to the weight of the body.
1.3. viscocity is affected by: temperature and density
2. Fricitional force
2.1. Frictional force is the force that opposes motion.
2.1.1. Static frictional force- required to just start a body. Kinetic frictional force- required to keep the body sliding.
2.2. Frictinal force is advantageous in: walking, moving vehicle, braking. Frictional force is disadvantageous since it causes wear and tear and generates unnecessary noice.
2.2.1. Ways of minimizing friction: use of ball bearing, use of rollers, lubricating.
3. Newton's third law
3.1. It states that for every action there is an equal but opposite reaction force.
3.2. Formula for the lift:When the lift is moving upward (accelerating R=m(g+a) . When the lift is moving downward (decelerating) R=m(g-a) When the lift is at rest/moving with uniform acceleration R=mg.
3.2.1. m-mass,g-gravitational pull,a-accelerarion
3.3. Elastic collision- type of collision in which both momentum and kinetic energy are conserved. Bodies move either in the same or different directions. Inelastic collision- type of collision in which momentum is conserved but kinetic energy is not. Bodies fuse and move in opposite directions.
3.3.1. Note: the total kinetic energy after the impact is always less than the total kinetic energy before the impact and the loss is due to: Energy used in deformation of bodies Energy transformed to heat, sound and even light
4. Newton's first law( law of inertia)
4.1. It states that a body remains in its state of motion or at rest unless acted upon by an external force.
4.2. Inertia- tendancy of a body to remain in its state of rest.
4.2.1. It is necessary for passengers to wear seat belts due to ineria force. When a car stops abruptly a person sitting in a moving car may be pushed forward causing accidents.