Agenda

• 1. Into to Newton’s Laws

• 2. Using Newton’s Laws to build a smart barrier

• 3. Experiment

• 4. Final Conclusions

An object in motion stays in motion and an object at rest stays at rest unless acted upon by an outside force

• For every action there is an equal and opposite reaction

I need ya’ll to come up with one reason for each law why a person would be injured during this crash…..

Newton’s First Law :

Newton’s Second Law:

Fly through the windshield because a person keeps going unless acted upon by an outside force (concrete wall, windshield, tree, seatbelt or airbag)

The force exerted on a car depends on the mass and acceleration involved… the massive deceleration of a crash unleashes a huge amount of force on the wall or other object that is hit……….

Newton’s Third Law :

…. The force exerted by the car on the wall= the force exerted by the wall back on the car… we can calculate this using the video

1.Car was moving with a velocity of 70 mph(30.8 meters per second)

2.Car went from 30.8 m/s to zero in .016 seconds (average impact time for smart car)

3. Acceleration= Final Velocity-Initial Velocity = 0-30.8 = -1925 m/s/s

Time .016 S

4. Force= Mass x Acceleration= 730 kg(smart car mass) x 1925 m/s/s

1,405,250 newtons of force exerted on the car. If I stood on your head I would exert about 700 newtons of force. Imagine 2000 times more force!

• What are two ways we can decrease the force on a car?

1. Decrease Mass of the Car

2. Decrease acceleration on impact…. How do we do this?

Acceleration= Vf-Vi

t

If we keep velocity the same what could we change to diminish deceleration………

INCREASE STOPPING TIME!

• Name two things in your car that slows you down during a car crash?

1. Seat Belts

2. Airbags

Airbags act like an air baggy barrier, their thickness slows down your head as it flies forward and it also prevents a collision with the steering wheel

• Today you are going to perform an experiment to see if a barrier that you build yourself can slow down a car enough to decrease impact force.

Homemade Crash Barrier Experiment

Question: What will happen to the force on a car when it collides with

a concrete wall if a homemade barrier is placed in between the car

and wall?Hypothesis(will the force increase

or decrease):

Materials• 1. one friction car• 2. kg weights for mass• 3. sturdy clay, about a half a cup or one stick• 4. 10 straws• 5. 1 meter of masking tape• 6. 10 cotton balls• 7. 10 Popsicle sticks• 8. 10 x 10 cm square of aluminum foil• 9. At least a 30 cm ramp• 10. concrete block• 11. 3-4 cm ruler with mm visible• 12. electronic balance• 13. one half popsicle stick

Method

• 1. First of all you need to figure out how much force is exerted on the friction car when you crash it into the wall without a barrier.

• Run five trials with this setup:

MethodA. Find end of friction car with longest edge from wheel. B. Make one tube of clay into a square and place it on edge of friction car so

that a centimeter or two is hanging overC. Place half popsicle stick into clay so it is sturdy, mark point where clay

and stick overlap with pencilD. I advise you add mass to car. Now use electronic balance to find the

entire mass of the system, write this in your data tableE. Place ramp on half concrete blockF. Bottom of ramp should be at least 25 cm from brick collision wallG. Place car with its back wheels at the top of the ramp and releaseH. The popsicle stick will collide first with wall and should penetrate the clay

even more. Mark again where the sick and clay overlap. I. Take stick out and measure the displacement of the stick…use a mini-

ruler to find the displacement in millimeters. Place this in your data table under trial 1.

J. Repeat four times and then average.

Building Method

• You will now build a barrier out of the limited supplies given to you.

• You will test if the barrier decreases the displacement of the stick

• Run five trials with your barrier and average

• Write your interpretation of the data• Answer the conclusion questions the best

you can