Question

physics webquest - newtons first law & force diagrams
directions: respond to the questions below. you may type, write, and/or draw your answers.
complete sentences are not required for every question, but your answer should be thorough to
demonstrate understanding of the concepts. no response should be copied word for word
from the websites.

1. define newtons first law of motion in your own words (your definition must be complete!)
2. there are many applications of newtons first law of motion. several applications are listed

below - provide a short explanation for each application below.
a. blood rushes from your head to your feet when riding on a descending elevator, which
suddenly stops.
b. to dislodge ketchup from the bottom of a ketchup bottle, the bottle is often turned upside
down, thrust downward at a high speed and then abruptly halted.
c. headrests are placed in cars to prevent whiplash injuries during rear - end collisions.

1. click on the following link:

http://www.physicsclassroom.com/mmedia/newtlaws/cci.cfm, read the text, and watch the
animation. then respond to the questions below:
a. if a car collides with a wall, what occurs to a passenger who is wearing a seat belt?
b. if a car collides with a wall, what occurs to a passenger who is not wearing a seat belt?

Explanation:

1. Newton's First Law of Motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

2.
a. When the elevator suddenly stops, the blood (which was in motion) continues to move downward due to inertia (tendency to keep moving as it was).
b. The ketchup in the bottle is in motion when the bottle is thrust downward. When the bottle is abruptly halted, the ketchup continues to move downward (due to inertia) and dislodges from the bottom.
c. During a rear - end collision, the car suddenly moves forward. The head (due to inertia) tends to stay in its original position. The headrest provides a force to prevent the head from moving backward (whiplash).
3.
a. If a car collides with a wall and the passenger is wearing a seat belt, the seat belt applies a force on the passenger. According to Newton's First Law, the passenger would have continued moving forward (due to inertia). The seat belt stops the passenger from moving forward (reduces the impact).
b. If the passenger is not wearing a seat belt, the passenger will continue to move forward (due to inertia) at the speed the car was moving before the collision. The passenger may hit the windshield or other parts of the car interior.

Answer:

1. An object remains in its state (rest or uniform motion) unless an unbalanced force acts on it.

2.
a. Blood has inertia; continues moving down when elevator stops.
b. Ketchup has inertia; continues moving down when bottle stops.
c. Head has inertia; headrest provides force to counteract.
3.
a. Seat belt stops passenger (force acts against inertia).
b. Passenger moves forward (due to inertia) and may hit interior.