circular motion

• What is a radian?

  A measure of an angle
• How do you convert degrees to radians?

  Multiply by $\pi$ and divide by 180
• How do you convert radians to degrees?

  Multiply by 180 and divide by $\pi$
• What is the radian equivalent of 360 degrees?

  2$\pi$ radians
• What is the radian equivalent of 180 degrees?

  $\pi$ radians
• What is the radian equivalent of 90 degrees?

  $\frac{\pi}{2}$ radians
• What is the time period in circular motion?

  Time to complete one full circle
• How is frequency related to time period?

  Frequency is one over the time period
• How do you calculate the velocity of an object in circular motion?

  Velocity = $\frac{2\pi r}{t}$
• What does angular velocity represent?

  Angular displacement over time
• How is angular velocity calculated?

  $\omega =$$\frac{2\pi}{T}$
• How can angular velocity also be expressed in terms of frequency?

  $\omega =$$2\pi f$
• How are linear velocity and angular velocity related?

  $v =$$\omega r$
• What is the formula to convert rpm to radians per second?

  Multiply by $2\pi$ and divide by 60
• How many radians per second is 200 rpm?

  Approximately 21 radians per second
• What is a centripetal force?

  Net force causing circular motion
• What are the two key features of centripetal force?

  Directed towards center and perpendicular to velocity
• What is the formula for centripetal force?

  $F =$$\frac{mv^2}{r}$
• What is centripetal acceleration?

  Acceleration towards the center of rotation
• What is the formula for centripetal acceleration?

  $a_c =$$\frac{v^2}{r}$
• Why can linear speed be constant while linear velocity changes in circular motion?

  Direction changes while speed remains constant
• Why does the speed of an object in circular motion not change?

  Net force is perpendicular to motion
• What is the work done by centripetal force?

  Work done is zero
• How can we express centripetal force in terms of angular velocity?

  $F =$$m\omega^2 r$
• How can we express centripetal acceleration in terms of angular velocity?

  $a_c =$$\omega^2 r$
• What is the procedure for investigating circular motion in an experiment?

  • Spin a mass on a string
  • Keep radius constant
  • Vary mass and measure weight
  • Measure radius with a ruler
  • Time multiple oscillations
  • Calculate velocity and plot force vs. velocity squared
• What does the graph of force against velocity squared indicate?

  It should be a straight line through the origin
• How can we determine the mass of the object from the graph?

  Gradient equals mass divided by radius
• What happens to the normal reaction force in circular motion at an angle?

  It has vertical and horizontal components
• How does the normal reaction balance weight in circular motion?

  Vertical component balances weight
• What provides the centripetal force in a car turning left?

  Horizontal component of normal reaction
• How do we derive the speed in circular motion at an angle?

  Using two equations and cancelling mass
• What is the formula for speed in circular motion at an angle?

  $v =$$\sqrt{g r \tan \theta}$
• What are the forces acting on an object in vertical circular motion?

  Weight and normal reaction
• How do forces act in position one of vertical circular motion?

  Weight and normal reaction are in the same direction
• How do forces act in position two of vertical circular motion?

  Weight and normal reaction are in opposite directions
• What is the normal contact force in position one?

  $r =$$\frac{mv^2}{r} - mg$
• What is the normal contact force in position two?

  $r =$$\frac{mv^2}{r} +$$mg$
• Where is the normal contact force greatest in vertical circular motion?

  At position two
• What should students do after this revision lesson?

  • Complete past paper questions
  • Ensure understanding of circular motion
  • Review all concepts thoroughly