CRECALL

Result of experimentRadius (mm)

Time (s) Period Distance (m)

Speed (m/s)

Trial 1 600 40 8 1.88 0.05

Trial 2 400 35 7 1.26 0.05

Trial 3 300 20 4 0.94 0.05

Questions:•What makes the car revolve from the center?•What do you think will happen if the string is cut?

Centripetal ForceThe centripetal force is the force that is center-seeking, it maintains the circular path of an object.

Play

Questions:•What have you noticed with the objects shown in the video?•What makes those objects keep their circular path?•Is there any other factor that helps such objects to do what they are actually doing?

CHANG A PENNY

Questions:1. What makes the penny to be remained attached to the hanger while the hanger is rotating?2. Which of the materials exerts centripetal force?

C

CENTRIPETAL ACCELERATION

AND FORCE

Objectives1.Define centripetal force and centripetal acceleration2.Cite objects where centripetal force exists3.Solve problems involving centripetal force and

acceleration

Centripetal AccelerationChange in velocity per unit of time in a uniform circular motion

Always directed towards the center of the curvature“center-seeking” accelerationMagnitude of tangential velocity is the same as the magnitude of tangential speed but both have different direction

Formulaor

- centripetal acceleration (m/s2)v- tangential speed (m/s)r- radiusw- rotational speed (rad/s)

Centripetal ForceIt is the “center-seeking” forceIt is the force that maintains the circular path of the object.

FormulaFrom

F=ma

Centripetal force becomesFc = m ac

Fc – centripetal forcem- massac – centripetal acceleration

Using tangential and rotational speed…

or

Sample problem:Solve for the centripetal force of an 8000kg train whose speed is 100km/h that rounds a curve whose radius is 150m.

ReflectionSince the centripetal force talks about a circular

motion and an object traveling a circular path will continue to have its path as long as the centripetal force is present, this means an endless thing and a cycle that you will go back from where you started. Sometimes in life, when work seems to be endless and problems keep coming back, we need to persevere more and be patient. It has never been easy to be patient, but it’s probably harder now than any time in history. Have you tested your patience? How? What does it bring you? Is it true that patience is a virtue?

Seatwork:1.What is the centripetal force of a point on the rim of

a 0.90m flywheel in diameter, turning at the rate of 1200rad/min?

2.If the weight of a car traveling with a speed of 100km is 1.44 x 104 then the radius is 150m, what would be the necessary force?