Download 4 impulse momentum FR File

Student _________________ Class ___________ Date ____________ Momentum & Impulse 1 9 Momentum is a vector defined as the product of the mass and velocity of an object 9 Momentum has dimensions mass x length/time, and its SI units are kilogram‐meters per second ( · / ) 9 Momentum is a vector quantity, so you must specify both its size and direction 9 A small object moving with a very high velocity (i.e. a bullet) may have a larger momentum than a more massive object that is moving slowly (i.e. a bike) does 9 Small hailstones falling from very high clouds can have enough momentum to hurt someone or cause serious damages to cars and buildings 9 If you are coasting down a hill on your bike you will accelerate, in other words, you are “picking up speed” or “gathering momentum” 9 Impulse is a vector defined as the product of force and time interval over which the force acts on an object: ∆ 9 A change in momentum takes both force and time 9 Impulse‐momentum theorem says that: Force x time interval = Change in momentum ∆
∆
9 Remember, we need a simple convention to describe the direction of vectors 9 We have been using negative speed for objects moving left or down (west or south) and a positive speed for objects moving right or up (east or north) 9 When a hitter hits the baseball coming from the pitcher he hits the ball as hard as possible over a very small interval of time to change the momentum of the ball 9 When a baseball player catches a ball in the field he travels with the ball as much as possible to increase the time interval and to decrease the force of impact 9 Stopping times and distances depend on the impulse‐momentum theorem 1. A 2,250 kg pickup truck has a velocity of 25 m/s to the east. What is the momentum of the truck? 2. A deer with a mass of 146 kg is running head‐on with a speed of 17 m/s. You are going north. Find the momentum of the deer. 3. 4. 5. 6. A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the northwest. a) What is total momentum of the child and the bike together? b) What is the momentum of the child? c) What is the momentum of the bike? A 1,400 kg car moving westward with a velocity of 15 m/s collides with a utility pole and is brought to rest in 0.30 s. Find the force exerted on the car during the collision. An 82 kg man drops from rest on a diving board 3.0 m above the surface of the water and comes to rest 0.55 s after reaching the water. What is the net force on the diver as he is brought to rest? A 0.40 kg soccer ball approaches a player horizontally with a velocity of 18 m/s to the north. The player strikes the ball and causes it to move in the opposite direction with a velocity of 22 m/s. What impulse was delivered to the ball by the player? 7. 8. 9. A 0.50 kg object is at rest. A 3.00 N force to the right acts on the object during a time interval of 1.50s. a) What is the velocity of the object at the end of this interval? b) At the end of this interval, a constant force of 4.00 N to the left is applied for 3.00 s. What is the velocity at the end of the 3.00 s? A 2,240 kg car traveling to the west slows down uniformly from 20.0 m/s to 5.00 m/s. a) How long does it take the car to decelerate if the force on the car is 8,410 N to the east? b) How far does the car travel during the deceleration? A 2,500 kg car traveling to the north is slowed down uniformly from an initial velocity of 20.0 m/s by a 6,250 N braking force acting opposite the car’s motion. a) What is the car’s velocity after 2.50 s? b) How far does the car move during 2.50 s? c) How long does it take the car to come to a complete stop?