1. Newton’s Laws Acceleration
November 7, 2017
Newton’s Laws
Acceleration

2. Drill - Take out Homework
m = 35 kg Fnet = ??? a = ??? μ = ???

3. Practice – Example 1
A 63 N force is applied to pull a 67-kg box across the floor at a constant speed of 0.48 m/s left. What is the coefficient of friction?
Identify knowns/unknowns
Draw free body diagram
Find the magnitude of all forces in free body diagram
Answer the question – what is μ?

4. Practice – Example 2
A person pushed horizontally to the right with a force of 220 N on a 38 kg crate to move it across a floor. The coefficient of kinetic friction is What is the acceleration of the crate?
Identify knowns/unknowns
Draw free body diagram
Find the magnitude of all forces in free body diagram
Find Fnet
Answer the question – what is a?

5. A box of bananas with a mass of 5. 00 kg rests on a desk
A box of bananas with a mass of 5.00 kg rests on a desk. The coefficient of static friction between the box and the desk is 0.400, and the coefficient of kinetic friction is
How much normal force does the horizontal surface exert on the box of bananas?
If no horizontal force is applied to the box and the box is at rest, how large is the friction force exerted on the box?
How great is the friction force if a horizontal force of 6.0 N is exerted on the box and the box is initially at rest?
What is the minimum force that will start the box in motion?

6. Static vs Kinetic Friction
Static Friction will EQUAL the Applied Force (up to the max Static Friction) and the object will stay at rest.
The Applied Force must be LARGER than the MAX Static Friction to make the object move.
Once the object begins to move, the friction is now Kinetic Friction.