2. WHAT ARE THE FORCES?
A FORCE IS ANY ACTION CAPABLE OF PRODUCING ANY DEFORMATION IN THE
BODIES ON WHICH IT ACTS OR ALTERS ITS STATE OF REST OR MOVEMENT. IN
THE INTERNATIONAL SYSTEM THEY ARE EXPRESSED IN NEWTON (N).
3. CLASSIFICATION OF MATERIALS ACCORDING TO THE EFFECT OF
THE FORCES
● RIGID: DO NOT MODIFY THEIR FORM WHEN A STRENGTH ACTS ON THEM.
● ELASTIC: RECOVER YOUR ORIGINAL FORM WHEN YOU STOP ACTING THE
FORCE THAT DEFORES YOU.
● PLASTICS: AFTER CEASING THE FORCE THAT DEFORES THEM, THEY DO
NOT RECOVER THEIR PRIMITIVE FORM AND THEY ARE DEFORMED.
5. FORCES DEFORM THE BODIES
ONE OF THE EFFECTS OF THE FORCES IS THE CHANGE OF THE FORM OF THE
BODIES, THE DEFORMATION OF AN ELASTIC BODY (FOR EXAMPLE A SPRING)
IS DIRECTLY PROPORTIONAL TO THE FORCE APPLIED, OR WITH OTHER
WORDS, THE GREATER THE FORCE APPLIED THE MORE IT WILL DEFORM THE
BODY,
6. HOOKE LAW
THE LAW VIEWED IN THE PREVIOUS SLIDE IS THE HOOKE LAW:
F = K ● (l - l0)
WHERE:
● F IS THE FORCE THAT CAUSES THE DEFORMATION AND EXPRESSES IN
NEWTON (N).
● K IS THE CONSTANT OF THE ELASTICITY OF THE OBJECT, AND IT IS
MEASURED IN
N / m.
● l-l0 DEFORMATION, CHANGE OF LENGTH, AND MEASURE IN m.
7. EXERCISES
1. A SPRING IS SUSPENDED FROM ONE OF ITS EXTREMES. IF WE PUT ON THE
OTHER END WEIGHTS THAT EXERCISE A FORCE OF 25 N, THE SPRING IS
ALARGED 5 ● 10-3 m. CALCULATE:
A) THE ELASTIC CONSTANT (K) OF THIS SPRING.
B) THE EXTENSION OF THE SPRING IF WE PUT WEIGHTS THAT EXERCISE A
FORCE OF 40 N.
2. WE APPLY A FORCE OF 9 N TO A SPRING AND THIS IS ALARGED 2.5 cm.
HOW MUCH WILL IT BE EXTENDED IF WE APPLY ONE OF 20 N?
8. FORCES DEFORM THE BODIES
DO NOT CONFUSE THE TERMS MASS AND WEIGHT:
-THE MASS IS THE AMOUNT OF MATTER THAT HAS A BODY AND IS MEASURED
IN Kg.
-THE WEIGHT IS A FORCE AND IS MEASURED IN NEWTONS (N).
-WEIGHT = MASS X GRAVITY
-THE FORCES AMONG THEM THE WEIGHTS ARE MEASURED WITH THE
DYNAMOMETER, A TUBE WITH A GRADUATED SCALE, AND WITH AN ELASTIC
SPRING IN ITS INTERIOR.
10. WHAT IS THE MOVEMENT?
A BODY IS MOVING IF IT CHANGES POSITION WITH RESPECT TO THE
SELECTED REFERENCE SYSTEM. IF YOU DO NOT CHANGE THE POSITION
WITH RESPECT TO THE REFERENCE SYSTEM, YOU WILL BE IN A REST.
THE REFERENCE SYSTEM WILL BE THE POINT OF SPACE FROM WHERE WE
LOOK AT THE MOVEMENT OF THE BODY.
A BODY IN MOTION IS DESIGNATED MOBILE.
11. THE ELEMENTS OF THE MOVEMENT
TO DESCRIBE THE MOVEMENT OF A MOBILE, WE USE 4 ELEMENTS:
THE POSITION (X): IT IS THE PLACE THAT A MOBILE IN A SPECIFIED MOMENT
OCCUPIES IN THE SPACE, WITH RESPECT TO THE REFERENCE SYSTEM.
THE PATH: IT IS THE WAY FOLLOWED BY THE MOBILE TO GO FROM THE
INITIAL POSITION TO THE FINAL POSITION. THAT IS, IT IS THE LINE THAT JOINS
THE SET OF POINTS DESCRIBED BY THE MOBILE IN ITS MOVEMENT.
TIME (t): IT IS THE ONE THAT TAKES A MOBILE IN TRAVELING A DETERMINED
DISTANCE.
DISTANCE TRAVELED (S): IS THE SPACE TRAVELED BY A MOBILE.
12. SPEED
• THE SPEED (v) IS THE DISTANCE THAT A MOBILE TRAVELS IN A UNIT OF
TIME, AND INDICATES THE RAPIDITY OF THE MOVEMENT.
Speed (V) = space (s) / time (t)
• THE INSTANT SPEED IS THE SPEED OF THE MOBILE IN A DETERMINED
INSTANT.
• THE AVERAGE SPEED IS THE AVERAGE OF ALL INSTANT VELOCITIES.
13. EXERCISES
1. THE FAMOUS RUSSIAN PILOT CURRO NOVELLOV HAS EXCEEDED THE
SNAIL CAREER RECORD WITH A MARK OF 35 MINUTES THE KILOMETER.
WHAT SPEED WAS ITS SNAIL? EXPRESS THE SPEED IN METERS / SECOND.
2. MAIKEL RAMIREZ IS A CELEBRATING REGGAETON SINGER WHO ON HIS
LAST TOUR HAD TO PASS THROUGH THE ATLÁNTICO (6750 KM) AT A HALF
SPEED OF 210 KM / H IN HIS PRIVATE JET TO ARRIVE IN TIME TO HIS CONCERT
IN ALMOGÍA. WHAT TIME THE TRAJECT CARRIED OUT?
3. THE DANCER OF THE RUSSIAN BALLET NOELIA NAVARRETILOVA IS
FAMOUS IN THE WHOLE WORLD FOR ITS DELICACY AND RAPIDITY OF
MOVEMENTS. IT DOMINATES LIKE ANY THE DEMIPLIE, PERFORMING IT AT A
SPEED OF 15 M / S. IF DURING THE LAST PERFORMANCE, YOU DONE THIS
STEP FOR A ACCUMULATED TIME OF 2 MINUTES WHAT DISTANCE DID YOU
VISIT BY PERFORMING THE DEMIPLIE?
15. THE UNIFORM RECTILINE MOVEMENT (MRU)
A MOBILE MOVES WITH UNIFORM RECTILINE MOVEMENT (MRU) IF IT
FOLLOWS A RECTIFINE TRAJECTORY AND ITS SPEED IS CONSTANT AT ALL
TIMES.
AS THE SPEED WILL NOT VARY, THE MEDIUM SPEED AND THE INSTANT
VELOCITY OF THE MRU MATCH AT ALL TIMES DURING THE MOVEMENT.
THE MRU CAN ALSO BE EXPRESSED GRAPHICALLY:
IN THE GRAPHICS SPACE-TIME, THE MRU WILL APPEAR TO BE REPRESENTED
BY A STRAIGHT, WHICH WILL PRESENT GREATER INCLINATION WHEN THE
SPEED IS GREATER. WE ALSO DIFFERENTIATE TWO CASES: WHEN THE
SPEED IS POSITIVE AND WHEN THE SPEED IS NEGATIVE.
17. GRAPHICS OF MRU
IN THE TIME-SPEED GRAPHICS, THE MRU WILL APPEAR TO BE REPRESENTED
BY A STRAIGHT WITHOUT PENDING. WE CAN ALSO DIFFERENTIATE BETWEEN
POSITIVE SPEED AND NEGATIVE SPEED:
18. EXERCISE
1. SEE THE NEXT SPACE-TIME GRAPH. KNOWING THAT IT IS A MOBILE IN A
UNIFORM RECTILINE MOVEMENT, CALCULATES SPEED AT THE BEGINNING
OF THE GRAPH (POINT 0,0), AND POINTS X1, X2, X3, X4.
19. ACELERATION
ACCELERATION IS THE VARIATION OF SPEED BY UNIT OF TIME, AND
INDICATES THE RAPIDITY WITH WHICH A MOBILE CHANGE OF SPEED. YOUR
UNIT IN THE INTERNATIONAL SYSTEM IS m / s2.
• IF ACCELERATION IS POSITIVE INCREASES THE SPEED.
• IF ACCELERATION IS NEGATIVE, THE SPEED IS DECREASED.
20. ACELERATION
LA ACELERACIÓN ES LA VARIACIÓN DE VELOCIDAD POR UNIDAD DE TIEMPO,
Y NOS INDICA LA RAPIDEZ CON LA QUE UN MÓVIL CAMBIA DE VELOCIDAD.
• SI LA ACELERACIÓN ES POSITIVA AUMENTA LA VELOCIDAD.
• SI LA ACELERACIÓN ES NEGATIVA DISMINUYE SU VELOCIDAD.
25. FORCE AND MOVEMENT
1st LAW OF NEWTON OR LAW OF INERTIA: EVERY BODY REMAINS IN REST OR
WITH CONSTANT RECTILINE MOVEMENT IF ON HIM NO FORCE ACT ON IT.
THE INERTIA IS THE TENDENCE OF A BODY TO MAINTAIN ITS STATE OF REST
OR MOVEMENT.
2nd NEWTON LAW OR FUNDAMENTAL PRINCIPLE OF THE DYNAMIC: THE
FORCE THAT ACTS ON A BODY AND THE ACCELERATION THAT PRODUCES
THIS BODY ARE DIRECTLY PROPORTIONAL, THAT IS, IF THE FORCE APPLIED
IS GREATER, THE ACCELERATION ACHIEVED WILL BE GREATER.
F = m ● a
26. EXERCISES
1. CALCULATES THE ACCELERATION THAT ACQUIRES A BODY OF 50 KG
THAT MOVES ON A HORIZONTAL SURFACE WHEN A FORCE OF 200 N IS
APPLIED.
2. CALCULATES THE FORCE TO BE APPLIED TO A MASS BLOCK OF 100 KG
SO THAT ITS ACCELERATION IS 1.25 m / s2?
3. WHAT IS THE MASS OF A BODY IF BY APPLYING A FORCE OF 360 N IT
CAUSES AN ACCELERATION OF 1.8 m / s2?
