Acceleration and net force

  1. As an object falls freely near the surface of the Earth, its velocity:
    a:decreases b:increases
    c :remains the same
    • What is b: increases
    • •The velocity increases at 9.81 m/s every second!?
  2. A car starts from rest at 4.0 m/s2 . The car will reach a speed of 28 m/s at the end of:
    a:3.5 s b:7.0 s
    c:14 s d:24 s
    • What is b: 7.0 s ?
    • a = v / t
    • 4.0 m/s2 = 28 m/s – 0 m/s / t t = 28 m/s / 4.0 m/
  3. A car moving at a speed of 8.0 meters per second enters a highway and accelerates at 3.0 meters per second2. How fast will the car be moving after it has accelerated for 56 meters?
    a:24 m/s b:20 m/s
    c:18 m/s d:4 m/s
    • What is b: 20 m/s ?
    • Vf2 = Vi2 + 2ad
    • = ( 8m/s )2 + 2 ( 3m/s2 ) ( 56m)
    • = 400 m2/s2
    • Vf = 20 m/s
  4. A toy projectile is fired from the ground vertically upward with an initial velocity of +29 meters per second. The projectile arrives at its maximum altitude in 3.0 seconds. As the projectile rises and then falls back to the ground, its acceleration
    a:decreases, then increases
    b:increases, then decreases
    c:increase only d:remains the same
    What is d: remains the same?

    All objects fall at a constant acceleration of 9.81 m/s2 unless friction is present?
  5. An object, initially at rest, falls freely near the Earth's surface. How long does it take the object to attain a speed of 98 meters per second?
    a:.1 s b:10 s
    c:98 s d:980 s
    • What is b: 10 s ?
    • vf = vi+ at
    • 98 m/s = 0 m/s + 9.8 m/s2 t
    • 98 m/s = t
    • 9.8 m/s2 10 s = t
  6. Which is a scalar quantity?
    What is? mass
  7. The force the counteracts on gravity is called
    What would be the normal force?
  8. In a vacuum, if an elephant and a feather fall from a high tree, which one will encounter the greater force of air resistance while falling to the ground?
    What would be that neither would experience air resistance?
  9. Which results in acceleration of an object, balanced or unbalanced forces?
    unbalanced forces
  10. When an object is in equilibrium, the net force is
Card Set
Acceleration and net force
midterm 2