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Forces and Motion Review. Define Force. A push or pull on an object. What is a net force?. Total amount of force applied to an object. What is the weight of a 20 kg dog?. W=20kg * 9.8m/s² W= 196N. What is the unit of measure for weight and force?. Newton.
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Define Force • A push or pull on an object
What is a net force? • Total amount of force applied to an object
What is the weight of a 20 kg dog? W=20kg * 9.8m/s² W= 196N
A porsche 911 accelerates from rest to 4.7m/s². the mass of the car is 1400 kg. What is the average net force that acts on the Porsche? F=MA F= 1400 * 4.7 F= 6,580 N
Name the 4 types of Friction • Static • Rolling • Sliding • Fluid
Why don’t objects stay moving horizontally forever? • Gravity and air resistance
What type of friction is Air Resistance? • Fluid friction
Describe what happens when an object reaches terminal velocity • The object is no longer accelerating; force of gravity is equal to the force of air resistance
A bulldozer pushes a 60kg crate with a force of 180 n. The force of friction on the crate is 60 n in the opposite direction. What is the acceleration of the box? 120N=60kg* a 120/60=a 20m/s²=a
Define projectile • An object in which the only force acting is gravity
An empty airplane has a mass of 30,400 kg and a takeoff acceleration of 1.20m/s².What is the net force accelerating the plane? • F=MA • F=30,400 * 1.2m/s² • F=36,480 N
What is another name for Newton’s first Law? • Law of Inertia
Define Inertia • Resistance of an object to change its motion
Using a vector arrow, what does the length of the arrow represent? • The magnitude (strength)
How can you tell which direction the net force Is being applied? • The head of the arrow points in the direction of the force
How does a balanced force affect the motion of an object? • Motion is unchanged if the force is balanced
Define speed • The distance traveled over a certain amount time
How are speed and velocity different? • Speed is a scalar quantity (magntude only) and velocity is magnitude and direction
What happens to an object’s acceleration when a force is increased? • The acceleration increases
How are Mass and inertia related? • The greater the mass the greater the inertia
Two tugboats are moving a barge. Tugboat A exerts a force of 3000 N to the right. Tugboat B exerts a force of 5000 N in the same direction. What is the Net Force on the Barge? ( Use Arrows to illustrate individual and net Force on the Barge)
How does surface roughness affect Friction? • The rougher the surface the greater the friction
A car is traveling at 50mph. How long will it take the car to travel 300 miles? • 300/50 T=6 hrs
IF you double the force exerted on an object how do you keep the acceleration the same? • Increase the mass
How are action and reaction forces related according to Newton’s third Law? • Reaction forces are of equal force to the action but in opposite direction
How does an unbalanced force affect an object’s motion? • It changes the speed or direction
What is the weight of a rocak that has a mass of 7kg? F=M*A F= 7 * 9.8 F=68.6 N