Potential Energy
What type of energy is stored due to an object’s position or height?
What is potential energy?
What type of energy is associated with motion?
What is Kinetic Energy?
What does Newton’s 1st Law say about objects that are not moving?
They will stay at rest unless acted on by an unbalanced force
what does F = ma mean?
Force = Mas x Acceleration
The downwards force that is always acting on us on Earth. (NB 31)
What is gravity?
If you lift a ball higher off the ground, does its potential energy increase or decrease?
What is increases?
What two factors affect an object’s kinetic energy?
Mass and speed
A property of matter that resists change in motion. (NB 29)
What is inertia?
What does Newton’s 2nd Law tell us about how force, mass, and acceleration are related?
More force causes more acceleration, and more mass causes less acceleration.
The sum of all forces. (NB 29)
What is net force?
Two identical books are placed on different shelves. One is higher than the other. Which has more gravitational potential energy and why?
The one on the higher shelf, because PE increases with height
Two identical carts roll at different speeds. Which has more kinetic energy and why?
What is The faster cart
The speed of an object that is moving but has a net force of 0. (NB 32-33)
What is constant speed?
If you push two objects with the same force, which will accelerate more — the lighter one or the heavier one?
The lighter one, because it has less mass.
The force a SURFACE exerts on an object. (NB 31)
Normal force
What two factors determine an object’s gravitational potential energy?
What is Mass and height (and gravity)
If two objects move at the same speed, which one has more kinetic energy — the heavier one or the lighter one?
The heavier one
More mass = more ____ (NB 29)
What is inertia?
If you use more force to push the same object, what happens to its motion?
It accelerates faster.
Unit to measure force. (NB 29)
What is a Newton?
True or False: Potential Energy can be converted to kinetic energy. (NB 34)
True
True or False: At the moment an object is falling and hits the ground, PE is at its highest and KE is at 0. (NB 38)
False
The speed of an airplane when the force forward is 12,000N and the air resistance backwards is 11,000N. (NB 33)
What is acceleration?
If an object isn’t accelerating, what can you say about the forces acting on it?
The forces are balanced (net force is zero).
An arrow that shows magnitude and direction of a force. (NB 29)
What is a vector?
Compare the potential energy of a rock on a cliff to one halfway down — which has more and why?
The rock on top has more because it’s higher, so it has more stored energy due to gravity
Why does a moving car have more kinetic energy than a bike going the same speed?
Because the car has more mass, and kinetic energy increases with both mass and speed.
If a soccer ball is rolling on the ground, why does it eventually stop even if no one touches it?
Friction is an unbalanced force that slows it down.
Why can you throw a baseball farther than a bowling ball?
The baseball has less mass, so the same throwing force gives it more acceleration.
What happens when balanced forces act on an object?
The object stays still or keeps moving at a constant speed
Which has more potential energy — a heavy ball on a low shelf or a light ball on a high shelf?
The light ball on the high shelf, because it’s higher up, and height increases potential energy.
What must happen to an object for its kinetic energy to change?
Its speed or mass must change (it has to speed up or slow down).
Why does a hockey puck slide farther on ice than on grass?
There’s less friction on ice, so inertia keeps it moving longer.
When a grocery cart starts moving faster after you keep pushing it, what is changing?
The acceleration is increasing because the force is still being applied.
What kind of force slows things down as they move across a surface?
Friction
When you climb to the top of a tall slide, why do you have more potential energy than when you’re at the bottom?
Because you’re higher above the ground, so gravity has more stored energy to pull you down.
When a skateboarder goes down a ramp, what happens to their kinetic energy?
It increases as they speed up going downhill.
When a magician quickly pulls a tablecloth and the dishes stay in place, what law is that showing?
Newton’s 1st Law — the dishes stay at rest because of inertia.
A book rests on a table. The Earth pulls down on it with gravity, but the book doesn’t fall. Why?
the forces are in equilibrium.
If you push on a wall and the wall doesn’t move, is there a force? Explain.
Yes, the wall pushes back with an equal and opposite force.