Journal P-5: Jumping Spider

1. Journal P-5: Jumping Spider A small spider, less than 2 cm in diameter, spots an insect. The spider crouches and crawls slowly forward. Then and leaps, landing right on the victim! A jumping spider has the amazing ability to jump 10-40 times its body length. To capture prey from that far away, it has to accurately estimate its beginning velocity. Once the spider jumps, the force of gravity controls its motion. , causing it to follow a curved path. Its velocity changes at every point along its path until it lands on its prey. • Once the spider jumps and is in the air, can it change its course? Explain. • Does the direction of motion change throughout its flight? Explain. • Think of an activity or sport in which the goal is to hit a specific target from far away. What are some of the challenges?

2. A. Force

3. 1. Force – push or pull • It has the ability to change an object’s motion • Starting • Stopping • Speeding up • Slowing down • Changing direction

4. Forces have both size and direction a. Size • Size is measured in SI units called newtons (N) • with a Spring Scale • b. Direction: • Same direction: Add (+) • Diff. direction: Subtract (-)

5. 3. Net force= combination of all forces acting on object • 4. Force is shown with vector arrows (remember these?). • they point in the direction of force • arrow length or thickness shows the strength of a force

6. For example:

7. 5. Forces can be.. • Balanced • No movement • Net force=0 • Unbalanced • Movement

8. 6. Calculating Force requires multiplying the mass and acceleration of an object: • F=ma=N • Variations • m=N/a • a=N/m

9. Practice-in your journals! 1. How much force is required to accelerate a 50 kg mass at 2 m/s2? 2. What is the acceleration of an 18 kg mass pushed by a 9 N force? 3. A truck is moving with a force of 100 N and an acceleration of 5 m/s2, what its mass?

10. Lab: The Nail Challenge You will receive one block and 12 nails. Your challenge is to balance 11 nails on 1 nail head. You may work in pairs using only the materials given and –of course-the normal force of gravity. GOOD LUCK!

11. B. FRICTION • Definition-it is a resistance to motion because of the force that two surfaces exert on each other 2. Can make moving easier or harder 3. Depends on 2 things • Type of surface • How hard the surfaces push against each other

12. 4. 4 main types a. slidingfriction-when solid surfaces slide over each other.

13. b. rolling friction-whenan object rolls over a surface. Until sliding friction takes him out!

14. c. fluid friction-when objects move through air or water. Adding lubricants can change sliding friction into fluid friction. Air resistance is fluid friction.

15. d. static friction-acts on objects that are not moving. It holds them in place until a force cause motion.

16. C. Gravity- an attractive force between two masses 1. Mass and distance are 2 factors that affect gravity • A big distance between things needs a –big force • A small distance between things needs smaller force • The larger the mass, the greater the gravitational force on an object • Also depends on Weight

17. So what is the difference between mass and weight? Mass : How much matter is in something. Never changes unless we cut off parts. Weight: a measure of the force of gravity in newtons

18. 3. Free Fall • Objects with gravity as the only force • Objects accelerate in free fall at the same rate of 9.8 m/s 2

19. 4. air resistance –a force that opposes the movement of an object in air • It is a type of fluid friction • Depends on size , shape and speed Remember your paper lab?

20. Remember most objects will hit the ground at the same time-if there is no air resistance.

21. 5. Terminal Velocity-theconstant acceleration of a falling object • increased speed=increased air resistance until ….. air resistance=force of gravity 6. Projectile Motion- a curved path that is caused by the downward pull of gravity and the initial force of velocity

22. 7. Vacuum – empty space • All objects fall at the same speed because there are no forces present. • In space, the spacecraft and astronauts are falling “around the Earth” at the same speed. This is why they experience weightlessness

23. D. PRESSURE • pressure is the amount of force acting on a surface • pressure equals force divided by area • p = f/a 3. Fluid Pressure-in air and liquids.

24. 4. Air Pressure • air pressure is caused by the motion of particles in the air • you do not feel the weight of the air because the pressure inside your body is equal to the air pressure around you • Barometer-instrument used to measure air pressure • Changes with altitude-gets lower as you go higher

25. 5. Water Pressure • Manometer-instrument used to measure pressure in liquids • the force of water pressure on an object is the same in all directions *This is why we don’t explode • water pressure changes with depth-the deeper you are, the greater the water pressure

26. d. Buoyant force • The ability of a fluid to have an upward force. This force is usually equal to the amount of fluid displaced by an object in it (like a boat) • This determines whether something sinks or floats (Archimedes's Principle) • The density of an object is a factor too. Density> 1will sink. A density < 1 will float.

27. 6. Bernoulli’s principle a. Bernoulli’s Principle-principle that states that as the speed of a fluid increases, its pressure decreases • b. airplane wings are designed to use Bernoulli’s principle • air traveling over the wings moves faster than air underneath • this reduces the pressure on top of the wing, allowing it to be pushed upward

29. c. Gravity (acting on mass=weight) pulls down on a plane but three forces combine to help an airplane fly • the upward force on a plane’s wing is called lift • a forward force, or thrust, helps the plane take off and maintain air speed • the air resistance on a plane is called drag