Newton’s Law Test

Newton's Laws

Part 1: Newton's Laws

Label the Law with the Correct Number:

Block A

Third Law (a): Every action has an equal and opposite reaction. All forces come in pairs.
Second Law (b): The formula for force is given as ( F = ma ); this states that a force is needed to cause a mass to accelerate.
First Law (c): Inertia: objects in motion tend to stay in motion unless acted upon by an outside force.

Questions

What are the units for force?
- Units of force are called Newtons.
Which has more inertia?
- A soccer ball with a mass of 1kg (no) or a bowling ball with a mass of 10kg (yes)
Which has more inertia?
- A car driving at 20 mi/hr (no) or a car driving at 60 mi/hr (yes).
A 10 kg bag of rocks is accelerated at a rate of 7.2 m/s² across the floor.
- a. What force is exerted to reach that acceleration?
  - Calculation using F = ma:
  - ( F = 10 \text{kg} \times 7.2 \text{m/s}^2 = 72 \text{N} )
- b. If the SAME force is applied to a 5 kg bag, what would you expect to be different?
  - With the same force (72 N), the acceleration will be higher for the 5 kg bag since ( a = \frac{F}{m} ), leading to ( a = \frac{72 \text{N}}{5 \text{kg}} = 14.4 \text{m/s}^2 ).
A person steps on a skateboard and it rolls back while the person only goes forwards a small amount.
- This scenario shows the Third Law of Motion: For every action (person pushing off the skateboard), there is an equal and opposite reaction (skateboard moves in the opposite direction).
A person pushes a round object with a force of 50N. If the mass has a mass of 400 kg, what force does it exert back on the person?
- According to Newton's Third Law, the round object exerts back 50N of force on the person.
A balloon car works because the air pushing out the back powers the car forward.
- a. Which of Newton's Laws helps to explain this scenario?
  - Third Law of Motion helps explain this scenario.
- b. Explain your reasoning.
  - Action: air pushing out the back of the car; Reaction: car moves forwards.
A person is driving down the road at 60 mi/hr when suddenly a car stops short in front of them. They slam on the brakes and are thrown forward.
- a. Which of Newton's Laws helps to explain this scenario?
  - First Law of Motion (Law of Inertia).
- b. Explain your reasoning.
  - The body continues moving forward due to inertia until stopped by the braking force.

Part 2: Forces and Force Diagrams

Fill in the Blanks:

The force that is the result of a surface pushing back on an object is called normal force.
The attraction straight down of all objects toward Earth is called gravitational force.
The force that slows motion and is always opposite to an object's motion is friction.
The leftover or result of combining all of the forces acting on an object is the net force.
Unbalanced forces cause an object to accelerate.
Forces always come in pairs.

Combining Forces:

For each of the pictures shown to the right, find the Fnet.

a) Fnet = 20N (Right, 10N + 10N)
b) Fnet = 0N (Equal forces in opposite directions cancel each other out)
c) Fnet = 10N (Assuming a third force opposing a 20N force)

Part 3: Gravity and Tides

Questions

The two factors that impact how much gravitational force there is are mass and distance.
Which picture best shows the gravitational force between the Sun and Earth?
- a) <10
- b) O-
- c) I chose my answer because the forces are proportional to their masses and the distance between them.
True or False:
- a) If the Earth moved CLOSER to the Sun, there would be MORE gravitational force. (True)
- b) If the Sun got smaller in mass, there would be MORE gravitational force. (False)
- c) Full moons and new moons result in higher than usual high tides. (True)
- d) Tides are a result of the moon's gravitational pull on the Earth. (True).
Which two moon phases lead to the highest high tides and the lowest low tides?
- Full Moon and New Moon phases
Draw the TWO alignments of the Sun, Moon and Earth that would result in the highest high tides.
- A) Full Moon alignment: Sun, Earth, Moon
- B) New Moon alignment: Sun, Moon, Earth