<p>Resultant velocity practice problems</p><p>1. Ann is at the airport and is in a rush. She normally travels north at 2 m/s. If she gets on a “moving sidewalk “ that travels at 2 m/s north and walks on it, what will be her resultant velocity? Ann = 2m/s north Sidewalk = 2 m/s north They are the same direction so you add velocities. 2 m/s + 2m/s = 4m/s North</p><p>2. Ann is still traveling north in the airport. She has two choices, take a place and stand on a north moving sidewalk at 2 m/s or to walk north at 3m/s on the empty south “moving sidewalk” that travels at 2m/s? Which choice is faster?</p><p>North sidewalk Ann= 0 m/s Sidewalk = 2 m/s north 0 + 2m/s = 2m/s north</p><p>South sidewalk Ann = 3m/s north Sidewalk = 2 m/s south They are in opposite directions so you subtract velocities 3m/s north – 2m/s south = 1 m/s north</p><p>Standing on the north sidewalk is faster</p><p>3. An action hero is running on top of a train traveling at 55m/s. If our hero is moving toward the front of the train at a speed of 5 m/s, what is our hero’s resultant velocity? Train = 55 m/s forward Hero = 5 m/s forward The directions are the same so this is an addition problem 55m/s =+ 5 m/s = 60 m/s forward.</p><p>4. You are on a bus traveling 47 m/s forward. You go to the back of the bus to visit your friend you are walking at a speed of 3 m/s. What is your resultant velocity? Bus = 47 m/s forward You = 3m/s to the back Your directions are opposite so you subtract 47m/s- 3m/s = 44m/s forward Acceleration problems- The formula for acceleration is (final velocity – starting velocity)/ time</p><p>1. A race car is traveling 150 m/s north. 30 seconds later the car is traveling 200 m/s. what is the acceleration of the race car? Starting velocity = 150 m/s North Final velocity = 200m/s north Time = 30 s (final velocity – starting velocity)/ time (200m/s – 150m/s) / 30 s ( 50 m/s) / 30 m/s Velocity = 1.67 m/s/s north</p><p>2. The race car traveling at 300 m/s west slows down to a stop in 120 seconds. What is the acceleration of the race car? Starting velocity= 300m/s west Final velocity = 0 m/s ( stop) Time = 120 seconds (final velocity – starting velocity)/ time (0m/s- 300m/s) / 120 s ( - 300m/s) /120s -2.5 m/s/s west ( Negative acceleration means slowing down or stopping)</p><p>3. You take a shopping cart that is not moving and race it down the grocery isle at 10 m/s in 3 seconds. What is your acceleration? Starting velocity = 0 m/s Final velocity = 10 m/s Time = 3 s (final velocity – starting velocity)/ time (10m/s – 0 m/s) / 3 10 m/s / 3s 3.33 m/s/s forward ( if no direction is given the direction is forward)</p><p>4. You are riding your bike down the bike path at 10 m/s When you come up to a hill that speeds you up to 15 m/s as you go down it. If the hill takes 13 s to go down what is you acceleration? Starting velocity = 10 m/s Final velocity= 15 m/s Time= 13 s (final velocity – starting velocity)/ time ( 15m/s – 10 m/s) / 13s (5 m/s) / 13 s 0.38 m/s/s forward 5. You are riding you bike north at a constant speed of 5 m/s. What is your acceleration? Starting velocity= 5 m/s Final velocity = 5 m/s Time – not given (final velocity – starting velocity)/ time</p><p>5-5 = 0 you can’t divide into 0 so even if a time was given the answer is that this is not acceleration</p><p>6. A lion runs eastward at a velocity of 30 m/s. two seconds later, it tackles it’s prey to the ground. What is the lion’s acceleration? Starting velocity = 30 m/s Final velocity = 0m/s ( to the ground indicates it is no longer moving) Time = 2s (final velocity – starting velocity)/ time ( 0m/s-30 m/s)/ 2 s ( - 30 m/s) / 2 s - 15 m/s/s forward Make sure you r answer is negative!</p><p>Net force questions</p><p>1. Two forces are acting on an object one has a magnitude of 12 N and is directed to the north. The other has a magnitude of 7 N and is directed to the south. The object experiences a net force of …. Force 1 = 12 N north Force 2 = 7 N south Opposite directions is subtraction 12 N north – 7N south = 5 N north</p><p>2. What is the net force of when you combine a force of 15 N north and 12 N north? Force 1= 15 N north Force 2 = 12 N north Both forces are in the same direction so you add them 15N north + 12 N north = 27 N north</p><p>3. What is the net force when you combine a force of 15 N north with a force of 12 N south? Force 1 = 15 N North Force 2 = 12 N south Forces are in opposite directions so you subtract them 15 N North- 12 N south = 3 N North 4. Two dogs are playing tug of war. The big dog exerts a force of 8N. The smaller dog exerts a force of 4 N. Who wins the tug and by how much? Big dog = 8 N Small dog = 4 N Tug of war means opposite directions which is subtraction</p><p>8N ( big dog ) – 4 N small dog = 4 N big dog wins</p>