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Physics Fall Semester Review

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  • T/F: An object's acceleration is ALWAYS in the same direction as the net force.
    True
  • Are acceleration and mass of an object directly or inversely related? (hint: F=ma)
    inversely
  • Which is greater 95 kg or 950 g?
    95 kg because 95 kg = 95000 g and 950 g = 0.95 kg
  • If a baseball is thrown into the air, is the displacement positive or negative when the velocity is zero?
    velocity is zero at the peak of the path (parabolic curve), at this point displacement is positive
  • What must be true about acceleration and velocity if an object is speeding up?
    acceleration and velocity must be in the same direction
  • Describe what is happening to the velocity if an object moves with an acceleration of -5 m/s/s?
    the velocity decreases by 5 m/s every second
  • If the frictional force is greater than the applied force is the object speeding up or slowing down?
    slowing down
  • What is the formula for calculating the gravitational force on an object?
    F=mg (F=m x -9.8)
  • The acceleration of an object directly relates with the ____ of the object.
    weight
    velocity
    mass
    force
  • When an object is thrown up in the air what is its acceleration?
    gravity (-9.8 m/s/s)
  • What is Newton's 2nd Law?
    F = ma
  • What do you know about the velocity if the forces on an object are balanced?
    velocity is constant
  • How do you decide which kinematic equation to use?
    use the equation that does not include the variable for which you have no information
  • What does the slope of a displacement (position) v. time graph tell you?
    velocity
  • T/F: When a model rocket is launched into the air and then falls back down to Earth the acceleration is changing?
    False; the acceleration is gravity (-9.8 m/s/s) the entire time
  • What does the slope of a velocity v. time graph tell you?
    acceleration
  • How do you calculate the weight of an object?
    weight = gravitational force = mg = m x -9.8
  • When a force of F is applied to an object with a mass of M it causes an acceleration of A. If the applied force is doubled (2F) what is the acceleration?
    2A (double)
  • What is the acceleration in all free fall (vertical kinematics) problems?
    gravity (-9.8 m/s/s)
  • The fastest speed skater in the world can accelerate from rest to 25 m/s in 15 seconds. What is the distance traveled during this time?
    187.5 m
  • What force typically opposes the gravitational force?
    normal force (sometimes tension force)
  • Name the force involving strings (or things similar to strings).
    Tension force
  • What is the displacement in the first 1s?
    2.5 m (area under the v-t graph is equal to the displacement)
  • What must be true about acceleration and velocity if an object is slowing down?
    acceleration and velocity must be in opposite directions
  • Which is greater static friction or kinetic friction?
    static friction
  • At what time(s) did the object turn around (change direction)?
    1s and 7s (whenever the line for the v-t graph crosses the x-axis the object is changing direction)
  • T/F: If the acceleration is zero the object must be at rest.
    False: an object can be moving with any constant velocity not necessarily 0 m/s
  • What forces act on an object as it falls through the air?
    gravitational (down) and drag/air resistance
  • When a force of F is applied to an object with a mass of M it causes an acceleration of A. If the same force is applied to an object with a mass of 4M, what is the acceleration?
    A/4
  • What is 112 cm in meters?
    1.12 m
  • Is the car in the FBD speeding up or slowing down? How do you know?
    speeding up; Fnet =( 275+395)-560 = +110 N; Fnet is to the right and velocity is to the right --> object is speeding up
  • When an object is thrown up into the air what is the velocity at the highest point (peak of the parabola)?
    0 m/s
  • T/F: If an object has a velocity of -3 m/s it must be slowing down.
    False; -3 tells us the object is moving in the negative direction (left) we know nothing about whether it is speeding up or slowing down bc we do not know a
  • T/F: If the forces acting on an object are balanced the object MUST be at rest?
    False; balanced forces mean constant velocity, the constant velocity does not have to be 0 m/s
  • When an object is dropped what is the initial velocity?
    0 m/s