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Objective 5 Motion, Forces, and Energy

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## Objective 5 Motion, Forces, and Energy

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**IPC 4A – Calculate speed, momentum, acceleration, work,**and power in systems such as in the human body, moving toys, and machines.**Using the formula chart**1. Circle what you are asked to find 2. Underline given facts with numbers and units and write the symbol above it. 3. Identify the formula(s) you will use from the formula chart 4. Rearrange the formula for what you’re asked to find. 5. Put in numbers for symbols and solve. 6. Check that you answered the question asked.**Rearranging formulas**When a formula is not solved for the variable you are trying to find, then you need to rearrange it until your variable is alone on one side of the equation.**d**v t Rearranging formulas Example, the speed formula is: If you are given speed and time and want to find distance, what would the formula be?**d**v t d t t x v x d v x t t Rearranging formulas Here, you divided d by t. To move t to the other side, do the opposite, multiply by it. t cancels on the right side And you are left with the formula for d.**Speed and Velocity**How fast an object is traveling. Velocity has direction, speed does not.**Acceleration**The change in velocity If an object is moving at a constant speed, acceleration = 0 Negative acceleration (deceleration) means the object is slowing down.**Work**Using force to move an object a certain distance. If there is no movement, there is no work done. If distance = 0, work = 0 Does not depend on the time it takes to do the work**If Distance = 0,**then Work = 0.**Power**The rate at which work is done. More power means the same work can be done faster.**What is the power of this motor?**Power = Work/time Time = 5 s We must find the work first! Work = Force x distance = 10 N x 2m = 20 J Power = Work/time = 20J/5s =4 Watts**Momentum**The product of an object’s mass and velocity. Can be thought of as how difficult it is to stop a moving object. A stopped object has zero momentum.**Conservation of Momentum**In collisions, total momentum does not change. The momentum of the objects (together) before the collision is the same as the momentum of the objects (together) after the collision.**Distance vs. Time graphs**• In a distance vs. time graph, the slope of the line is the speed of the object. • If you have a horizontal line, the object is stopped.**Constant speed away from a point**Constant speed toward a point**The line gets less steep – slowing down**The line gets steeper – speeding up**Velocity vs. Time Graphs**• In a velocity vs. time graph, the slope of the line is the acceleration of the object. • In this type of graph, a horizontal line means that the object is moving at a constant speed.**Two ice hockey players are skating directly at each other.**The first has a mass of 87 kg and is skating at a constant speed of 2.6 m/s. The second skater has a mass of 78 kg. How fast must the second skater be skating in order to have a momentum similar to the first skater? A 2.3 m/s B 2.9 m/s C 3.4 m/s D 5.2 m/s**How much force is needed to accelerate a 1,300 kg car at a**rate of 1.5 m/s2? F 867 N G 1,950 N H 8,493 N J 16,562 N**An ant crawled from Point A to Point B in 4.0 seconds. To**the nearest tenth, what was the ant’s speed in centimeters per second? Assume the ant traveled 5.6 cm. 1.4 cm/s**The diagram represents the total travel of a teacher on a**Saturday. Which part of the trip is made at the greatest average speed? F Q G R H S J T**A car traveled 150 km in 2.5 hours. What was its average**speed in km per hour? Record and bubble in your answer on the answer document. 60 km/h**Which bike rider has the greatest momentum?**A A 40 kg person riding at 45 km/h B A 50 kg person riding at 35 km/h C A 60 kg person riding at 25 km/h D A 70 kg person riding at 15 km/h**IPC 4B – Investigate and describe [applications of]**Newton’s laws such as in vehicle restraints, sports activities, geological processes, and satellite orbits.**Forces**• Force can be defined as a push or a pull. • Forces can be balanced, which mean they are equal and opposite with no change in direction. If the forces on an object are balanced, it will either remain at rest or it will move at a constant speed in a straight line.**Unbalanced forces cause an object to accelerate (speed up,**slow down or change direction) in the direction of the largest force.**Friction is a force that acts in the opposite direction to**the motion of a moving object.**Newton’s Laws**Newton’s First Law: An object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an unbalanced force. • The Law of Inertia.**Newton’s Second Law:**• Force = mass x acceleration • For a constant force, if mass increases acceleration decreases • For a constant mass, if force increases, acceleration increases**The force on the ball and the force on the cannon are equal**(See 3rd Law). F = ma The ball’s mass is lower, so its acceleration is higher. The cannon’s mass is greater, so its acceleration is lower.**Newton’s Third Law: For every action force, there is an**equal and opposite reaction force.**In the event of an accident, air bags and seat belts may**help reduce injury to a passenger by decreasing the force that stops the passenger’s motion. The force is reduced because the seat belts or air bags decrease the — A mass of the passenger B acceleration of the passenger C reaction time of the driver D speed of the vehicle**The illustration above shows a student about to throw a**ball while standing on a skateboard. Which illustration below correctly shows the skateboard’s direction of motion after the student releases the ball?**The table shows times required for the same toy car to**travel 10 m across an identical section of a floor after it is pushed. The difference in times was probably caused by differences in — A force exerted B surface friction C air resistance D car mass**IPC 5A – Demonstrate wave types and their characteristics**through a variety of activities such as modeling with ropes and coils, activating tuning forks, and interpreting data on seismic waves.**Types of Waves**1. Transverse 2. Longitudinal (compression)**Calculating Wave Speed**Velocity of a wave = Wavelength • Frequency Measured in Hz