1. Acceleration and net force equations

2. Friday, 11/6 Unit 4: Forces
Respond to the following questions for both pictures.
1. Using your knowledge of inertia, describe how the image demonstrates Newton’s 1st Law of motion.
2. What could you do to change the motion of the bus or the race car?

3. Weight vs. Mass Mass is matter (atoms)
Weight is the force of gravity acting on mass.
Weight is represented by the symbol Fg
Fg will always act on an object.

4. How to Calculate force of gravity (weight)
Note: when calculating Fg acceleration will always be 10 m/s2

5. Example – calculating weight (Fg)
A child pulls a wagon with a mass of 6 kg, ten meters across the grass to the garage. The child applies a 10 N force to overcome 2Ns of friction. Calculate the weight of the wagon. G: m = 6kg E: Fg = (m)(a) S: 60 N U: Fg S: Fg = (6)(10)

6. Practice calculating weight (Fg)

7. Practice calculating weight (Fg)

8. How to calculate force Note: acceleration will not
Be 10 m/s2 unless the object
Is in free-fall.

9. How to Calculate net force

10. Newton’s 2nd Law – Practice problem 1
A car has a mass of 550 kg. 1. Find the weight of the car on Earth 2. Find the net force needed to accelerate the car at 12 m/s2. 3. If a net force of 2200 N were to act on the car, what would its acceleration be?

11. Newton’s 2nd Law – Practice problem 1
A car has a mass of 550 kg. 1. Find the weight of the car on Earth Fg = 5,500N 2. Find the net force needed to accelerate the car at 12 m/s2. Fnet = 6,600N 3. If a net force of 2200 N were to act on the car, what would its acceleration be? a = 4 m/s2

12. Newton’s 2nd Law – Practice problem 2
A sled weighs 2500 N on Earth 1. What is the mass of the sled? 2. What is the mass of the sled on the moon, where g = 1.6 m/s2? 3. What is the weight of the sled on the moon? 4. What net force is needed to accelerate the object at 4.0 m/s2 on the moon?

13. Newton’s 2nd Law – Practice problem 2
A sled weighs 2500 N on Earth 1. What is the mass of the sled? m = 250kg 2. What is the mass of the sled on the moon, where g = 1.6 m/s2? 3. What is the weight of the sled on the moon? Fg = 408.2N 4. What net force is needed to accelerate the object at 4.0 m/s2 on the moon? Fnet 1,020.4N

14. Net Force Equation Used to identify the net force on an object
X and Y components are independent of each other
End up with two net force equations, one in the x direction and one in the y direction
Opposing forces are subtracted and forces in same direction are added

15. Net Force Equation Example

16. 1b
Write net force equations for the x and y components.

17. 1b
Write net force equations for the x and y components.

18. 1e

19. 1e