- Speed is distance travelled by an object per unit of time
- speed=distance travelled / time
velocity is speed in a given direction; it therefore tells us two things about moving object: its speed and its direction
- The rate of change of velocity is called acceleration. Acceleration refers to any change of velocity, either positive or negative.
- acceleration= final velocity-original velocity / time
- Momentum an object traveling at a specific velocity has quantity called momentum.
- Momentum=mass x velocity
- p = mv EX. p = (2.0 kg)(4.0 m/s); p = 8.0 kg-m/s
Newton's first law
The law of inertia, states that objects in motion tend to stay in motion and that object at rest tend to stay at rest.
Newton's 2 Laws
- Newton’s second law describes the relationship between force, mass, and acceleration. It states that the force applied on an object equals the mass of the object times its acceleration.
- Force= mass x acceleration (F=ma).
Newton's 3 Law
The third law states that for every force there is an equal and opposite force. For example, if you push on a wall, it will push back on you as hard as you are pushing on it. The blast from the back of the rockets pushes the rocket forward.
- Density is a physical property of matter that is defined as the ratio of an object's mass to its volume.
- Energy is ability to do work
- kinetic energy
- Kinetic energy is energy associated with motion. Any moving body has this type energy because it is able to do work by moving other bodies.
- Kinetic energy = ½(mass x velocity)2
Potential energy is the energy stored in a body because of its position
- Work is defined as the product of the force applied to an object and the distance through which the force is applied. Work is the transfer of energy. Work has a specific definition in physics, it is equal to the force needed to move an object multiplied by the distance it moved.
- Work = Force x Distance
- How much work is done if a force of 20 N is used to displace an object 3 m? W = (20 N)(3 m)=60N-m. =60 Joules because 1 Joule is equal to 1 Newton-meter
A joule is the unit of energy equal to the work done by a force of 1 Newton acting over distance of 1 meter. One joule is the amount of energy it takes to lift an object that weighs one Newton a one meter distance.
- Power is rate at which work is done. The power of a machine is the total work done divided by the same time taken. Since work equals force times distance, the formula power is:
- Power = work/time
The six simple machines
The six simple machines are the lever, wedge, screw, inclines planes, wheel and axle, and pulley
An inclined plane is a simple machine. An inclined plane is a ramp used to reduce the effort needed to raise or lower an object over a vertical height.
A wedge (klin) is a moving inclined plane
A lever( richag) is a simple machine. A lever bar exerts a force to move a load by turning on a pivot or fulcrum
- Pulley is a chain or rope wrapped around a wheel
A wheel and axle
- A wheel and axle act as a lever that rotates in a circle
- A screw is an inclined plane wrapped around a cylinder