DAY 49

WARM-UP:

1. take a look at this chart. A. In this problem, what is the impulse always equal to? B. What happens to the force felt during the collision as the time of collision is increased?
   1. Combinations of Force and Time Required to Produce 100 units of Impulse

1. C. If you're boxing, and you know you're going to get punched, would it make more sense to:
2. flex your neck muscles so your head doesn't move when you get hit.
3. relax your neck muscles so your head moves when you get hit.

D. Why?

1. You’re in a car collision. Which of the following scenarios would be safer for your body?

1. Not sure how to answer this question?
2. A. Find the change in velocity for Case A and Case B
3. B. For which case would the change in momentum, or impulse, be smaller? What does that tell you?
4. From the Flipping Physics video, what is the benefit of wearing a helmet during a collision?

CLASSWORK:

#049A: Impulse/Change in Momentum Practice

Complete problems 1-7 (all) in the Check your Understanding section here --> LINK

#49B:

1. A 240.0-kg snowmobile accelerates, which results in a force being exerted that speeds up the snowmobile from 6.00 m/s to 28.0 m/s over a time interval of 60.0 s.
   1. A. Sketch the event, showing the initial and final situations.
   2. B. What is the snowmobile’s change in momentum? What is the impulse on the snowmobile?
   3. C. What is the magnitude of the average force that is exerted on the snowmobile?
2. A 2200-kg vehicle traveling at 94 km/h (26 m/s) hits a concrete wall. Suppose a 60kg person is driving the car. The velocity of the person equals that of the car both before and after the crash, and the velocity changes in 0.20 s. Sketch the problem.
   1. a. What is the average force exerted on the person?
   2. b. Some people think that they can stop their bodies from lurching forward in a vehicle that is suddenly braking by putting their hands on the dashboard. Find the mass of an object that has a weight equal to the force you just calculated. Could you lift such a mass? Are you strong enough to stop your body with your arms?

Learning at home (HW)

• (4:21) Demonstrating How Helmets Affect Impulse and Impact Force - EDpuzzle
• (3:59) Review of Momentum, Impact Force, and Impulse - EDpuzzle