Force Motion Energy

For an object to move, there must be an application of force. Force is a push or a pull that causes an object to move, change direction, change speed, or stop. Pull Push

Newton’s First Law of Motion An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by a force.

Applying force can cause motion, a change in the position of the object. Applied force caused a change in position of the car! Force

Energy is required to apply force. Energy is the ability to do work by applying force. Force was applied to lift the rocket into the air!

work- a change in temperature, speed, position, pressure, or form of matter as a direct result of energy applied in a system.

Two kinds of Energy Potential Energy - Stored energy Kinetic Energy - The energy of motion Let’s see what happens to the potential and kinetic energy of the biker as he goes up the hill! Force As the biker goes up the hill, kinetic energy decreases while potential energy increases. As the biker goes down the hill, kinetic energy increases while potential energy decreases. At the top of the hill, the biker has maximum potential energy but minimum kinetic energy. At this point, the biker has stored energy that can be used to go down the hill. Force

Potential Energy Potential energy depends on gravity. The higher the object, the more potential energy it will have. Ball about to be dropped has stored energy. Drawn bow has stored energy. Water at the top of a waterfall has stored energy. Compressed spring has stored energy.

Potential energy depends on height of the object. Lower weight: Lower potential energy → Rolls down and reaches bottom slower Larger weight: Higher potential energy → Rolls down and reaches bottom faster Higher height: Higher potential energy → Higher impact Lower height: Lower potential energy → Lower impact

Potential Energy converted to Kinetic Energy… When stored energy begins to move, the object transfers energy from potential energy into kinetic energy. Standing Running

Kinetic Energy Energy of motion. They all have kinetic energy! Jumping rope results in motion. Vibration of the telephone causes motion. They all have kinetic energy! Car going down the road has motion. Spinning a ball has motion.

Kinetic energy depends on an objects mass and velocity. Slower Speed: Lower kinetic energy → Slower acceleration Higher Speed: Higher kinetic energy → Faster acceleration Lighter Load: Lower kinetic energy → Easier to push/pull Heavier Load: Higher kinetic energy → Harder to push/pull

Measuring Energy Just like time, distance, and speed, energy can be measured. Energy is measured in joules (J). Joule- the unit used to measure energy. The amount of energy that is needed for a change within a system The sum of all mechanical energy = PE +KE.

Example in… I do not own Angry Birds.

What happens to the kinetic and potential energy of the bird as it is released?

While the bird is ascending, kinetic energy is decreasing and potential energy is increasing.

The bird is at the top of the trajectory The bird is at the top of the trajectory. At this point, kinetic energy is at a minimum while potential energy is at a maximum. What happens to the kinetic and potential energy of the bird as it falls back to the ground?

While the bird is descending from the top, the kinetic energy is increasing and potential energy is decreasing.

Let’s test our understanding of potential and kinetic energy!

Good job! The blue shirt skater has the lowest kinetic energy. Which skater has the lowest kinetic energy? The blue shirt skater has the lowest kinetic energy. Which skater is transferring energy from potential energy to kinetic energy? The red shirt skater is transferring from potential energy to kinetic energy. Which skater has the highest kinetic energy? The yellow shirt skater has the highest kinetic energy. Which skater has the lowest potential energy? The yellow shirt skater has the lowest potential energy. Good job! Which skater has the highest potential energy? The blue shirt skater has the highest potential energy. What is the order of sequence for increase in potential energy? The correct sequence is yellow, red, blue. What is the order of sequence for increase in kinetic energy? The correct sequence is blue, red, yellow.

Summary Potential and kinetic energy are two types of energy. Potential energy is stored energy. Kinetic energy is energy of motion. Both depend on mass of the object. Potential energy also depends on position of the object, while kinetic energy also depends on the speed of the object. Potential energy can be converted to kinetic energy, and vice versa. Potential and kinetic energy are measured in joules.

Fin!