Transcript Motion
Motion The motion of an object can be measured. The position of an object, its speed, and direction can be represented on a graph. (C.S. 2.1, 3.2) • Cheetahs are the fastest land mammals in the world! • It can cover 200 meters in 7 seconds (that is half a lap on the track) • It can accelerate from 0 to 29 meters per second in 3 seconds! • What does a cheetah have to do with our lesson? Motion & Speed • Motion is simply a change of position • Speed tells us how fast an object is moving. The more distance a cheetah covers in a given time, the greater his speed. • If a cheetah can travel at a speed of 100 km per hour and an ant can only cover 36 meters in an hour- The cheetah has a greater speed. Average Speed • Average speed= distance time Memorize this formula. You should already know it! Calculate the average speed • Suppose an airplane traveled 810 miles between two cities. The elapsed time for the trip was 3 hours. Calculate the speed of the airplane. Average speed= 810 miles 3 hours When you do the math the speed of the average speed of the plane is 270 miles per hour Speed doesn’t always use mph • Suppose a runner runs a race around a track that is 400 meters. If the runner runs the race in 40 seconds, what would be the runners average speed? Average speed= 400 meters 40 seconds Do the math and 400 divided by 40 is 10 mps Calculating Distance • Suppose you are taking a trip by car. You can travel about 50 mph on the roads you will be using. You also know you can travel about 6 hours per day. You would like to know how far you can go in one day. In other words you NEED TO CALCULATE DISTANCE Distance = speed x time Distance = 50 x 6 So the answer is 300 miles Calculating Time • Suppose you have a job marking the lines on the football field. The distance to be marked is 80 meters. You mark at a speed of 50 meters per minute. How much time will it take you to mark the whole line? Time= distance speed Time = 80 meters 50m per 1 min 80/50 =1.6 minutes First law of motion • Stop/Start – Friction – Gravity Newton’s first law of motion states that if no forces acts on an object at rest, it will remain at rest. The law also says that if the object is moving, it will continue moving at the same speed and in the same direction if no force acts on it. Second law of motion • Acceleration – Speed – Time Newton’s Second Law of Motion says that the amount of force needed to produce a given change in the motion of an object depends on the mass of the object. The larger the mass, the more force is needed to give it a certain acceleration. Third law of motion • Action • Reaction Newton’s Third Law of Motion says that if an object exerts a force on a second object, the second object will always exert a force on the first object. This forces will be equal to the force exerted by the first object. But the force will be in the opposite direction. This law is sometimes stated: For every action, there is an equal and opposite reaction. One last view of the cheetah • Finish your worksheet using the formulas we have learned today for – Average speed – Calculating time – Calculating distance