牛顿第一定律(英文版教案).pptVIP

Newtons First Law of Motion Law of Inertia Miha Lee Newtons First Law of Motion Every object in a state of uniform motion tends to remain in that state of motion unless an unbalanced force is applied to it. An object at rest An object in motion An Object at Rest An Object in Motion Galileos thought experiment I An Object in Motion Galileos thought experiment II Frictional force Friction is the force that acts on a moving object to slow it down and bring it to stop. Question 1: Evaluate the following assertion. If there is no frictional force on the road, cars can move without consumption of energy by the Newton’s first law of motion. So we can save energy. An Object in Motion A dynamic cart with a brick on it. Get it moving and stopped. Tape the brick to the cart. Get it moving and stopped again. Seat belts protect us from being hurt by keeping us tied to the vehicle. An Object in Motion Inertia The resistance an object has to a change in its state of motion. Question 2: What does the magnitude of inertial force depend on? F = ma m: inertial mass Application to everyday life Opening a bottle Removing dusts from cloths Seat belts Seismometer Seat Belt Seat belts can exert forces to cause passengers to slow down at the same rate as the vehicle. Question 3: How does a seat belt exert force on us? The principle of retractors * * *