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1、Force and MotionDefine mechanics, force and net force.lMechanics is the study of the motion of objects, and the related concepts of forces, accelerations, and energy.lA force is any kind of push or pull.lIt is a vector quantitylA force of 1 Newton is defined as the amount of force required to accele
2、rate a 1 kg at 1 m/s2lA net force is the vector sum of all the forces acting on a body.Recognize that the mass of a body is the characteristic that relates the force on the body to the resulting acceleration.lMass is the quantity of matter present in an object. lIt is also a quantitative measure of
3、the inertia of a body.lMass is a scalar quantitylMass is the characteristic of a body that relates the bodys acceleration to the net force causing the accelerationlInertia is the tendency of an object to resist changes in its motionState Newtons First Law and understand that it defines the kinds of
4、reference frames in which the laws of Newtonian mechanics hold.lNewtons first law (law of inertia) states that every body continues in its state of rest or of uniform speed in a straight line unless it is compelled to change that state by forces acting on it.lSimply stated this means that an object
5、at rest stays at rest and an object in motion continues at the same speed in a straight line until an unbalanced force acts on it.State Newtons First Law and understand that it defines the kinds of reference frames in which the laws of Newtonian mechanics hold.lThis means that Newtons first law expl
6、ains the motion of an object when only balanced forces (Fnet = 0) are acting.lIn other words if there is no net force acting on a body it remains at rest, or if it was moving it continues with constant speed in a straight line.State Newtons three laws of motionThe occupant of the car can be stopped
7、by a seatbelt, the wall, whatever is on the other side of the wall, etc. Next time you get in a car, you choose which one you want to stop you!lInertial frame of reference (non accelerating)- Newtons first law holds true. i.e. watching an Indy race from the grand stands.lAccelerating frame of refere
8、nce - Newtons first law does not hold true. i.e. watching an Indy race from the point of view of the driver or inside a freely falling elevator.lNewtons law of inertia does not describe the behavior of objects lA. In inertial frames of referencelB. Moving with constant velocity relative to a given f
9、rame of referencelC. At rest relative to a given frame of referencelD. Moving in accelerated frames of referencelE. Moving in a straight line at constant speed relative to a given reference frame.A ball bearing is shot into the spiral of tubing. When it exits the tubing, which path will it follow?Pa
10、th 3. After exiting the tubing, it will continue in a straight line since there is no net force acting on it.Click on Picture for the correct answerState Newtons Second Law in its scalar component version and apply it to the solution of dynamics problems.lNewtons second law, also known as the law of
11、 acceleration, states that the acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. l The direction of the acceleration is in the direction of the applied net force.State Newtons Second Law in its scalar component version and app
12、ly it to the solution of dynamics problems.la = acceleration (m/s2)lF = net force (N)lm = mass (kg)lIf the force is given as 2.0 N and the mass is 500 g, what acceleration will be given to the mass?l4.0 m/s2lCalculating the weight of an object is just a special case of Newtons second law. You will u
13、se the acceleration due to gravity as the acceleration in the equation.lThe weight vector is always towards the center of the earth since that is the direction of the acceleration due to gravity.lWeight is the gravitational force exerted by a large body (such as Earth). FW = mg. The acceleration of
14、gravity (g) on Earth is 9.8 m/s2.lAstronauts left a 500 kg rover on the moon where the acceleration due to gravity is 1.6 m/s2. lWhat is the mass of the rover on the moon?l500 kglWhat is the weight of the rover on the moon?l800 NlWhat was the weight of the rover on the earth?l4900 NlA body moves wit
15、h constant speed in a straight line. Which of the following statements must be true?lA. No force acts on the bodylB. A single constant force acts on the body in the direction of motionlC. A single constant force acts on the body in the direction opposite to the motion.lD. A net force of zero acts on
16、 the bodylE. A constant net force acts on the body in the direction of motionlA force accelerates a body of mass M. The same force applied to a second body produces three times the acceleration. What is the mass of the second body?lA. MlB. 3MlC. M/3lD. 9MlE. M/9lA net force of 64 N acts on a mass of 16 kg. The resulting acceleration islA. 16 m/s2lB. 0.51 m/s2lC. 64 m/s2lD.
