2 SpeedThe distance an object travels in a certain amount of time; describes a rateAverage speed – Total distance divided by total timeConstant speed - Speed that does not change
3 What is the formula for calculating speed? Speed equals distance divided by time.Unit of Measurement: meters per second (m/s), kilometers per hour (km/hr), or miles per hour (mi/hr)
4 SpeedSpeed = distance ÷ time t = d/Sd = S*td÷S X t
5 Let’s Practice Calculating Speed In your notebook, calculate this problem. Make sure you show all work!A football field is about 100 meters long. If it takes a person 20 seconds to run its length, how fast was the football player running?
6 Remember to label the UNITS!! Check Your WorkA football field is about 100 meters long. If it takes a person 20 seconds to run its length, how fast was the football player running?Speed = Distance ÷ TimeSpeed = 100 m ÷ 20 sSpeed = 5m/sRemember to label the UNITS!!
7 VelocityAn object’s speed and direction at a given time; describes a rate and how fast something movesThe wind is blowing 65 km/hr from the North.
8 AccelerationA change in the direction or speed (velocity) of an object over time – which may be:A change in speedStartingStoppingSpeeding up (positive acceleration)Slowing down (negative acceleration)A change in directionAcceleration is caused by unbalanced forces.
10 Motion A change in the position of an object Caused by force (a push or pull)
11 Force A push or pull on an object Measured in units called newtons (N) Measured with a spring scaleForces act in pairsTypes of Force:gravityelectricmagneticfrictionAir resistanceBalancedUnbalanced
12 InertiaAn object at rest will remain at rest until acted upon by an unbalanced force.An object in motion will remain in motion until acted upon by an unbalanced force.When all forces acting on an object are equal (balanced)
13 Balanced ForcesWhen all the forces acting on an object are equal (net force is zero)Balanced forces do not cause a change in motion.Balanced forces can change the physical properties of an object without changing its motion.
14 How Can Balanced Forces Affect Objects? Cause the shape of an object to change without changing its motionCause an object at rest to stay at rest or an object in motion to stay in motion (inertia)Cause an object moving at a constant speed to continue at a constant speed
15 Unbalanced ForcesWhen all the forces acting on an object are not equalThe forces can be in the same direction or in opposite directions.Unbalanced forces cause a change in motion.In your notes, describe an example of an unbalanced force.
16 How Can Unbalanced Forces Affect Objects? Acceleration is caused by unbalanced forces:slow downspeed upstopstartchange directionchange shapeIn your notes, describe an example of an unbalanced force affecting an object.
17 Net Force The total of all forces acting on an object: Forces in the same direction are added.The object will move in the direction of the force.Forces in opposite directions are subtracted.An object will move in the direction of the greater force.
18 Calculating Net Force10 N30 NA child was playing with a jack in the box. The lid pushed down with 10 N of force, while the spring pushed up with 30 N of force. What is the net force applied by the spring?In your notebook, calculate the net force and show all of your work.
19 Check Your Answer10 N30 NA child was playing with a jack in the box. The lid pushed down with 10 N of force, while the spring pushed up with 30 N of force. What is the net force applied by the spring?30 N up N down= 20 N up
20 Calculating Net Force Two competitors are playing tug of war. Tug of War Game30 N50 NTwo competitors are playing tug of war.What is the net force? Which direction will the rope move?In your notebook, calculate the net force and show all of your work.
21 Check Your Answer Two competitors are playing tug of war. Tug of War Game50 N30 NTwo competitors are playing tug of war.What is the net force? Which direction will the rope move?50 N to the right – 30 N to the left = 20 N to the right
22 Mass and Weight Mass is the amount of stuff (matter) in an object. The mass of an object will remain the same anywhere in the universe.Mass is measured in grams or kilograms.Weight is the mass (kg) of an object multiplied by the acceleration of gravity (9.8 m/s2).The weight of an object depends on the gravitational pull of the location in the universe.The gravitational pull on the Moon is only 1/6 of Earth’s gravitational pull.Weight is measured in newtons (N).
23 Mass and Weight A person with a mass of 25 kg x 9.8 m/s2 gravitational Example: F=maA person with a mass of 25 kg x 9.8 m/s2 gravitationalacceleration is equal to 245 N of weight force.F= 25 kg x 9.8 m/s2F = 245 NThe person exerts 245 N of force on the ground.If the person went to the Moon, they would only weigh 1/6of 245 N.
24 ForceForce (N) = mass (kg) x acceleration (m/s2)F÷m x a
25 ForceAcceleration (m/s2) = force (N) ÷ mass (kg)F÷m x a
26 ForceMass (kg) = force (N) ÷ acceleration (m/s2)F÷m x a
27 PracticeThe acceleration of a sprinter is 10 m/s2. The force exerted on the starting blocks is 650 N. What is the mass of the sprinter? Force = Mass = Acceleration =
28 Check Your AnswerThe acceleration of a sprinter is 10 m/s2. The force exerted on the starting blocks is 650 N. What is the mass of the sprinter? Force = 650 N Mass = 65 kg Acceleration = 10 m/s2 Mass = force ÷ acceleration Mass = 650 ÷ 10 Mass = 65
29 Practice A 56 kg cart is accelerating at 15 m/s2. Calculate the force exerted on the cart?Force =Mass =Acceleration =
30 Check Your AnswerA 56 kg cart is accelerating at 15 m/s2. Calculate the forceexerted on the cart?Force = 840 NMass = 56 kgAcceleration = 15 m/s2Force (N) = mass (kg) x acceleration (m/s2)Force = 56 x 15Force = 840
32 Check Your AnswerA boat is pulling a 54 kg wake boarder. The force the boatis exerting on her is 108 N. Calculate her acceleration.Force = 108 NMass = 54 kgAcceleration = 2 m/s2Acceleration = force ÷ massAcceleration = 108 ÷ 54Acceleration = 2