C3S2 Post Seat Belts, air Bags

Which object has the greatest

inertia?

• a) A 110-kg wrestler walking at 2 m/s.

• b) A 200-kg rock at rest.

• c) A 0.05-kg bullet flying at 400 m/s.

• d) A 50-kg girl sprinting at 8 m/s.

Two crash dummies of equal mass are

used to test seat belts. Dummy A has a wide seat belt and Dummy B has a

narrow seat belt. Both dummies are crashed into a barrier while in the

same car. Which of the following best describes the forces needed to stop

each dummy?

• a) Dummy A’s force is bigger than Dummy B’s.

• b) Dummy B’s force is bigger than Dummy A’s.

• c) The forces on the two dummies are equal.

• d) The forces cannot be compared unless you know how fast the car was moving.

Two crash dummies of equal mass are used to test seat belts. Dummy A has a wide seat belt and Dummy B has a narrow seat belt. Both dummies are crashed into a barrier while in the same car.

which statement below correctly

describes the pressure exerted by the seat belt on the dummies during the

stopping process?

• a) Dummy A’s seat belt exerts more pressure than Dummy B’s.

• b) Dummy B’s seat belt exerts more pressure than Dummy A’s.

• c) The seat belts exert the same pressure because the dummies have the same mass.

• d) The seat belts exert the same pressure because the dummies are in the same car.

When a rapidly descending elevator is

quickly stopped, blood tends to drain away from the head of a rider in the

elevator. Which of the following principles best describes this phenomenon?

• a) Objects at rest tend to remain at rest.

• b) Pressure varies with area and applied force.

• c) Interaction between two objects can result in an acceleration of one or both objects.

• d) Objects in motion tend to remain in motion with constant speed.

A 70-kg mass is moving at a constant

speed of 5 m/s in a straight line. When the mass begins to slow down,

which of the following must be occurring?

• a) The object must be losing some of its inertia.

• b) The object must be increasing its mass.

• c) A net force must be acting in a direction opposite the object’s motion.

• d) The object is slowing down because of its inertia.