The Nature of Force
A push or pull
What is force?
The force that two surfaces exert on each other when they rub against each other
Resistance to change in motion
What is inertia?
When the only force acting on an object is gravity
What is free fall?
Three
The SI unit of force
What is a Newton (N)?
A force that pulls objects toward each other
What is Newton's First Law of Motion?
An object at rest stays at rest and an object in motion stays in motion unless acted on by an unbalanced force?
A force that causes an object to move in a circular path
What is centripetal force?
A measure of the force of gravity on an object
The combination of all the forces on an object
What is net force?
Two factors that affect the gravitational force between two objects are
What are mass and distance?
The equation for Newton's Second Law of Motion
What is force= mass x acceleration (F=ma)?
Objects that orbit around other objects in space
Acts between objects that aren't moving
What is static friction?
Causes a change in the object's motion
Friction always acts:
a) in the same direction as motion
b) opposite the direction of motion
c) perpendicular to the direction of motion
d) at a 30o angle to the direction of motion
What is b) opposite the direction of motion?
If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first.
What is Newton's Third Law of Motion?
Satellites remain in orbit around Earth because:
a) the moon's gravitational pull on them is equal to the Earth's pull
b) no forces act on them
c) their motors keep them moving in circles
d) the curve of their paths as they fall matches the curve of the Earth
What is d) the curve of their paths as they fall matches the curve of the Earth?
Occurs when a solid object moves through a fluid
How can you find the net force of an object?
By adding together the strengths of all the individual forces acting on the object
Name 2 of the 4 different types of friction
Give a law of motion and a real-world example.
Answers vary. Examples may include:
A satellite orbiting Earth- 1st Law
Pushing a full shopping cart vs pushing an empty shopping cart - 2nd Law
Swimmer pushing the water pack and the water pushing the swimmer forward- 3rd Law
Towards the center of the circle an object is moving in
A 20 kg object accelerates at a rate of 5 m/s2. What is the net force acting on the object?
Force = mass (kg) x accerlation (m/s2)
Force = 20 x 5 = 100 Newtons (N)