Slide 1

APPLYING NEWTONS 2 ND LAW TO 1. Baby Newton Wasnt Expected to Live.. Body systems Reminder: FBDs and F net statements! Need we say more! When two objects are connected by a rope or chain, applying a force on one of the objects will cause both objects to accelerate at the same rate and in the same direction. We solve the question by assuming the applied mass is acting on a single object whose mass is equivalent to the Total Mass! Watch out for Neatorama facts on Sir Isaac Newton! Slide 2 Two body questions can be vertical or horizontal! Ex 1) Two blocks of identical material are connected by a light rope on a level surface. An applied force of 55 N [right] causes the blocks to accelerate. While in motion, the magnitude of the force of friction on the block system is 44.1 N. Calculate the acceleration of the blocks. Ex 2) Refer to the diagram above. The force of friction on the 10-kg block has a magnitude of 14.7 N. (a) Calculate the tension in the rope connecting the two blocks. (b) Calculate the tension in the rope between the hand and the 10-kg block. Since the boxes are attached by a wire, they must accelerate at the same rate. We can also treat them as one big mass instead of two small masses. We will assume that the wires have no mass. Fg and F N cancel each other vertically, so we can ignore them. To the right is positive, and to the left is negative. 2. Newton Almost Became a Farmer Slide 3 Two body systems contd Ex3) Two buckets of nails are hung one above the other and are pulled up to a roof by a rope. Each bucket has a mass of 5.0 kg. The tension in the rope connecting the buckets is 60 N. Calculate the acceleration of the buckets. Ex 4) Two boxes are attached by a thin wire as shown in Drawing 3. A person pulls on the wire attached to the yellow box. There is a force of friction of 213 N acting on the boxes. Determine the force applied to the boxes if they accelerate to the right at 2.45 m/s 2. 3. Newton and His Apple: The True Story Slide 4 Applying Newtons 2 nd law to Single Pulley Questions.. Atwoods Time! Atwood's Pulley is a classic physics problem involving two unequal masses hanging from a wire over a pulley. When m 1 = m 2, the machine is in neutral equilibrium regardless of the position of the weights When m 1 m 2 both masses experience uniform acceleration but in the direction of the larger mass. Ex 5) If mass one is 12.00 kg and mass two is 7.50 kg, determine the acceleration of each mass. We will need to be careful, since the net force is pulling the blue box down and the yellow box up, but is made up of two forces due to gravity pulling down on different sides. To simplify this, we will take our single mass and pretend that one forcedue to gravity is pulling it to the left, while the other force due to gravity is pulling it to the right. To be continued on Next Slide Slide 5 Example 5 Continued- Atwoods pulley 4. Newton was Secretive - He Rarely Published Slide 6 Offfspring of the Newtons Apple Tree in Woolsthorpe Manor Whatever happened to the mama tree? The Kings School in Grantham, Linconshire, England, where Newton went to school, claimed to have purchased the tree and moved it to its garden. Slide 7 5. Newton was Deeply Religious Ex 6) A 6.0 kg flower pot and a 4.0 kg flower pot are tied together and suspended from a pulley. A: 6.0 kg B: 4.0 kg a. What is the net force in the system? HINT! We must find the force on each pot And then find the net force on the system! b. what is the acceleration of the 6.0 kg pot? HINT: Because the pots are tied together we must use the total mass. c. what is the acceleration of the 4.0 kg pot? Slide 8 Remember to use total mass when calculating Fnet! Ex. 7) Two objects, A and B, are connected by a light rope over a light, frictionless pulley. A has a mass of 25 kg and B a mass of 35 kg. Determine the motion of each object once the objects are released. 6. He was an Alchemist! Slide 9 7. Newton Battled Counterfeiters Slide 10 Applying Newtons Second law to a Two- Pulley System Ex 8) 8. Newton the Politician Uttered Just One Sentence