Download presentation

Presentation is loading. Please wait.

Published byHubert Sharp Modified over 4 years ago

1
Newton’s Laws of Motion 1. If the sum of all external forces on an object is zero, then its speed and direction will not change. Inertia 2. If a nonzero net force is applied to an object its motion will change F= ma 3. In an interaction between two objects, the forces that each exerts on the other are equal in magnitude and opposite in direction. 30

2
Forces l Non-Contact ---- Gravity (F = G m M /r 2 ) è G = 6.7x10 -11 m 3 / (kg s 2 ) l Example: (two people) è F = (6.7x10 -11 ) (60) (60)/ (.5) 2 = è Weight of 100g = 31

3
Example Weight of Person l Calculate the gravitational force on a 60 kg person near the surface of the earth. l Earth: Mass = 6x10 24 kg, radius = 6.4 x10 6 m. F = G M m / r 2 = (6.7x10 -11 m 3 / (kg s 2 )) (6x10 24 kg) (60 kg)/ (6.4x10 6 ) 2 m 2 = kg m/s 2 (Newtons) l Most common gravitational calculation involves object close to surface of the earth è F = (G M / r 2 ) * m è F = * m = 33

4
Newton’s 2 nd Law l F net = m a What if Gravity is the only force?

5
Normal Force l Perpendicular to Surface l Repulsive l Reactive l Contact

6
Example: (person in elevator) M = 60kg Constant velocity

7
Example: (person in elevator) M = 60kg Accelerating up at 2 m/s 2

8
Example: (person in elevator) M = 60kg Accelerating down at 3m/s 2

9
Tension l Similar to normal force (Reactive) l Can only pull (can’t push on rope) l Constant throughout rope

10
Example: Box in Elevator 10kg a= 2 m/s 2

11
Springs l Similar to tension, normal l Reactive l Changes length according to tension l F = -k Δx 10kg k=50 N/m

Similar presentations

© 2019 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google