2. What happens if the force is increased? Do Now: 1. A copper block of mass 10 kg is being dragged horizontally across a steel table at a constant speed. What force is pulling the block? 2. What happens if the force is increased?

Practice A 10 kg box is pulled by a rope with 80 N force. The coefficient of kinetic friction is 0.2. Does the box move and which way? Draw FBD! What is the boxes acceleration? FF Fp = 80N m = 10 kg

Envelope Activity Use the information in your envelope to solve the question together as a group. Make sure to take any notes you might think are important.

Lauren is driving a car on an icy road with a constant velocity of 20 m/s. Her and the car have a combined mass of 1,500 kg. (Use rubber on ice for μ) What is the coefficient of friction? Draw a FBD for when the breaks are applied. What is the Force of friction when she hits the breaks hard to skid to a stop? How long does it take her to stop?

Example 1. Connor is trying pull wood across his wood floor to put into the fireplace. He pulls at a 30o angle with a force of 100 N. If the wood has a mass of 20 kg, will he be able to move it?

Individual Exercise Mike is dragging a sack of potatoes with a weight of 600N across the floor. The coefficient of static friction is .25 for the bag on the floor. If he pulls at 60o with a force of 200N, will the bag move?

Example 4 (advanced): What is the coefficient of friction of a tire on a level road if a car decelerates at a rate of 3 m/s2 once the driver takes her foot off the gas pedal? a = Fnet / m = Ff / m = µFN / m = µmg/m = µg 3 m/s2 = µ (9.8 m/s2) µ = 3 m/s2 / 9.8 m/s2 µ = .31

Review A crate is pulled with a NET force on a rough surface. Draw a FBD. If the Crate were filled, what would happen to the coefficient of friction? (Kinetic or static) If the crate were filled, what would happen to the Force of friction?