Force Basics
What is the definition of a force?
A push or pull
What unit do we use to measure forces?
Newtons (N)
Gravity is an ___________force.
A) Attractive (pulling)
B) Repulsive (pushing)
Attractive
Newton's 1st Law is Inertia. Define Inertia.
An object in motion will stay in motion and an object at rest will stay at rest unless acted on by an outside force.
Weight is a measurement of gravitational force on a certain mass. What is the formula for weight?
W=mg
Forces are represented by what symbol on a free-body diagram?
Arrows
Forces that go in opposite directions and have the same value are considered _____________ forces.
Balanced
Gravity pulls people towards the center of the Earth. What other force pushes back from the ground to keep us from moving downward through the ground?
Normal Force
Newton's 2nd Law tells us how to use force and mass to calculate the acceleration of an object. If an 5 kg object has a force of 20 N acted on it, what would be its acceleration? (Number and unit)
4 m/s2
F=M*A
Forces going in opposite directions are subtracted in order to find net force. What should we do with forces going in the same direction?
Add them.
A person pushes a box to the right with 5 N of force and another person pushes it to the left with 3 N of force. What is the net force? (Value and direction)
2 N to the right
What are the two things that affect the strength of gravity?
Mass and distance
Newton's 3rd Law deals with action reaction forces. These forces are applied between two objects. In order to follow Newton's 3rd Law, these forces must be _________ and __________.
Equal and Opposite.
The 'g' in the weight formula stands for the acceleration due to gravity. What is the numeric value of this variable?
9.8 m/s2
While most applied forces we have looked at are contact forces, gravity is an example of another type of force called a ____________ force.
Non-contact
Both teams pull on a rope during tug-of-war but one team is able to drag the other. These forces are considered __________ forces.
Unbalanced
Any two objects with mass have gravity pulling them toward each other. Why do we stick to the Earth but not to other objects?
The Earth has more mass which means more gravity.
Explain how you use Newton's 3rd Law in order to jump from the ground.
You push on the ground and the ground pushes back.
Friction
Draw a free-body diagram of a ball that is thrown to the right with 5 N of force, has 3 N of air resistance, and 2 N of gravitational force. Show ALL forces.
(Teacher Discretion)
An airplane has 30,000 N of lift (upward) force, 30,000 N of gravitational force, 15,000 N of forward force, and 10,000 of air resistance. What is the net force on the plane?
Hint: Draw the diagram.
5,000 N in a forward direction.
Gravity holds the moon in orbit around Earth. If the mass of the moon was to decrease, what might happen to the moon?
The moon might leave Earth's orbit because it would have less gravity.
When an object has a lot of mass but does not have much force applied to it, it will not accelerate much. This is due to which property of matter?
Inertia
One would think that gravity on a heavy truck might allow brakes to work more easily because it pushes the surfaces of the tires against the road harder, causing more friction. However, what other force actually makes it more difficult to stop a heavy truck from moving?
Inertia