Question

show what you know newtons 3 laws

1. identify the law from the given illustration

a:
b:

1. which of the following would change when an unbalanced force acts upon an object at rest?

a. the objects mass
b. the objects weight
c. the objects motion
d. the objects density

1. how quickly an object accelerates would depend upon what two things?

a. weight and mass
b. force and mass
c. motion and mass
d. none of these

1. forces that do not cancel each other out are known as ______________ forces.
2. newtons 3rd law deals with action - forces.
3. magicians often use the trick of pulling a table cloth out from under a table full of dishes without moving the dishes. which law would this be an illustration of and why?
4. when you are standing on a bridge, you are pushing down on the bridge but you dont fall through (hopefully!). which law would this be an illustration of and why?
5. when shopping, it is much easier to push the empty shopping cart than when it begins to fill up. which law would this be an illustration of and why?

Explanation:

1. The rocket illustration shows Newton's 3rd Law as the exhaust gases push down (action) and the rocket goes up (reaction).
2. An unbalanced force changes an object's motion according to Newton's 1st Law. Mass, weight and density are not directly affected by an unbalanced - force acting on a stationary object.
3. According to Newton's 2nd Law ($F = ma$), acceleration depends on force and mass.
4. Forces that don't cancel each other are unbalanced forces.
5. Newton's 3rd Law deals with Action - Reaction forces.
6. Pulling a table - cloth out from under dishes is an example of Newton's 1st Law (inertia). The dishes tend to stay at rest due to inertia.
7. Standing on a bridge without falling through is an example of Newton's 3rd Law. Your weight (action) on the bridge is balanced by the normal force (reaction) from the bridge.
8. Pushing an empty vs. full shopping cart is an example of Newton's 2nd Law. With the same force, a smaller mass (empty cart) has more acceleration than a larger mass (full cart).

Answer:

1. Newton's 3rd Law
2. c. the object's motion
3. b. force and mass
4. unbalanced
5. Reaction
6. Newton's 1st Law because the dishes have inertia and tend to stay at rest.
7. Newton's 3rd Law because your weight on the bridge is the action force and the bridge's normal force on you is the reaction force.
8. Newton's 2nd Law because with the same force, acceleration is inversely proportional to mass.