Hey, look again at the pictures of the two friends. What made Reymark push the table at a certain distance? He made it because he exerted a force on it. What do you mean by that? When you pushed something that means you applied a FORCE…or even when you pull something.. Clever!!! Hmm… even pulling something?
Congratulations! You are really learning a lot. You did a lot of work today.
Force - is a push or pull that produces motion, prevents motion and changes the direction of the motion of an object. It has both magnitude and direction and therefore, a vector quantity. Contact Force - a force between two objects (or an object and a surface) that are in contact with each other. N ON - CONTACT F ORCE - IS ANY FORCE APPLIED TO AN OBJECT BY ANOTHER BODY THAT IS NOT IN DIRECT CONTACT WITH IT. “Superb!!! The first reality is unfolded…”
Great! Now I know what force is and its two types. Really? How come they are related with each other??
Objective: To determine if there is a work done or no work done in the pictures. Directions: Put a check () whether the following pictures show a work done or no work done. 1. 2. Work done No work done
now, I understand that its not only force matters, if it is applied at angle, to lift upward the object, having a coefficient of friction along a horizontal surface but also the distance the object moved must be in the same direction. What? Say it now! Hurry up! Precisely! Your such a gifted modern James Prescott Joule ! But, another reality knocks my mind…Eppsss… I am going to treat you your favorite cheeseburger. How can we determine the amount of work done on the object?
That’s really a nice question. Maybe now, you’ve really understand the scientific definition of work. Of course! And ready to solve problems.. But…one last question please! What is that? Hurry up! What are those formulas and steps to follow? Ah, see! We have 4 formulas to consider. You mean, we’ll torn on to the next page?
Formul as of Work F x D Force x distance mgh Mass x acceleratio n due to gravity x height µ FnD Coefficient of friction x Normal F x distance Cos θ Fd Cosine θ x force x distance Expressed in Joules (J) 1Nm = 1J 1dyrecm = 1 erg In honor of James Prescott Joule
Step 4: Box your final answer. Step 3: Compute for the required. Step 2: Substitute the values. Step 1 : Write the given, required and formula to be used. Turn on to the next page.
Sample Problem: Suppose you pull your schoolbag with a force of 30 N parallel to the ground to your classroom 20m away. What is the work done in your bag? Let’s compute! Step1: Given F= 30Nd = 20m Step2: Required W =? Step3: FormulaW = Fxd = (30N)(20m) Step4: Final answer: = 600Nm Are you now ready to solve problems?
Objective: To compute for the work done in the given problems/situations. Problem 1: A man pushes his car with a force of 30N to the right. He moves the car at a distance of 3 meters to the right. What amount of work has he done? Problem 2: A loaded cart as shown in figure, was push along the handle of 30 o with the direction of motion and the cart moved through a distance of 6 m, how much work was done? Given: Required: Solution: Given: Required: Solution:
Problem 3: A book weighing 10N moves at a constant velocity along a horizontal surface having a coefficient of friction of 0.30. what is the work done on the book if it is moved at a distance of 0.5m? Given: Required: Solution: Problem 4: Suppos e a librarian lift a 1.5kg book from the lowest shelf in the cabinet to the fourth shelf 2m higher. What is the work done on the book? (assume g=9.8m/s²) Given: Required: Solution:
Though you’re hungry, we are still on the right track... Since we certainly did well today. Cheeseburge r !!! ??? Jollibee... Jollibee … have first a game… They are still on the right track… since they certainly did well today… Hmm.. Ehem.. Later for that, let us sum up first our learnings
I’ve learned that… Work Force Distanc e Contac t Non- contact Cos θ x Fd F x D µFnD Displace ment mgh Product of the force exerted on an object and the distance the object move If a force is applied at an angle At constant velocity, along a horizontal surface with coefficient of friction Lifting an object w/c is equal to the weight and gravity Is done only when a force is appli ed to a body and move s it.
____1. Which of the following forces is an example of a contact force? a.Gravitational forceb. Magnetic force c. Electric forced. Frictional force ____2. Which of the following are NOT examples of non-contact force? a.Gravitational forceb. Magnetic force c. Electric forced. Frictional force ____3.Which is the example of non-contact force in the following situations? a.Sun and planets gravitational pullb. sweeping the floor b.A ball rolling d. playing softball ____4. Non-contact force can also be termed as a.Action-Reaction Forcec. Air-Resistance Force b.Action-at-a-distanced. Frictional Force ____5. Contact force can also be termed as a.Action-Reaction Forcec. Air-Resistance Force b.Action-at-a-distanced. Frictional Force Directions: Choose the letter of the correct answer. Write your answer on the space provided before each number.
_____ 1. In which instance there is no work done in the system? a. a basket being lifted b. a person who stood in an ascending elevator c. a stone whirled around a horizontal circle d. a big box dragged along the floor _____ 2. Work can be defined as _______________. a. a vector quantity b. performed every time you exert force c. the product of the applied force and the time the force acts d. done only when an object moves some distance due to an applied force _____ 3. In which of the following situations work is done? a. lifting an object from the floor to the table top b. supporting an object on your head while standing in place c. pushing a concrete wall d. carrying a bag on your lap while seating ______4. From the pictures below, which situation/action show the presence of work? ______5. With the pictures below, choose which of the situation/action show the absence of work. a. b.c.d.
GOT IT ??? Let us all unfold the Reality of Work. “42 31 34 24 22 35 16 31 34 13 15 15 43 15 34 36 15 14 36 21 34 31 37 16 21 11 14 22 35 36 11 27 13 15.” Unlock the secret message in the golden scroll by using the code chart below.
E E E A V S P R N CR E How did you score? 5-15: Good 16-25: Very Good 26 or more: Excellent! Perseverance. Keep on trying! Work for it!
TTNEMECALPSID MUJEMEFALKIIH MTYODDOFXXSYZ EHHCUZRYMTRRC EHYGWLCWAVRCO SBXXITENTNVUS SBOBJECTLNGOI AXCPNEWTONOLN MOVENOITCIRFE Let’s do this fun activity, just try to hunt for words you think that has any relationship with work!!!
Given: F = 30N to the right d = 3m, to the right Required: W = ? Solution: W= F x d = (30N) (3m) = 90Nm or 90 J, to the right Given: Cos 30° = 0.866 F = 70N d = 6m Required: W = ? Solution: W = (F cos θ) d = (70N x 0.866) 6m =363.72 J
Given: Fn = 10 N d = 0.5 m µ = 0.30 Required: W=? Solution: W = µ Fn d (0.30)(10 N)(0.5) = 1.5J Given: m= 1.5 kg g= 9.8 m/s² h=2m Required: W=? Solution: W= mgh =1.5 kg)(9.8m/s²)(2m) = 29.4 Nm