circular motion

• What is the focus of today's revision lesson?

  Major concepts in circular motion
• How do you convert degrees to radians?

  Multiply by $\pi$ and divide by 180
• 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 per unit time
• What is the formula for angular velocity?

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

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

  $v =$$\omega r$
• How do you convert from rpm to radians per second?

  Multiply by $2\pi$ and divide by 60
• What is the angular displacement for 200 rpm?

  About 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 an object in circular motion have constant speed but changing velocity?

  Direction of velocity is constantly changing
• Why does the speed of an object in circular motion not change?

  No work done by the centripetal force
• What is the work done by a centripetal force?

  Zero work done
• 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 connected by a string
  • Keep radius constant
  • Vary the mass
  • Measure mass with a balance
  • Calculate weight providing centripetal force
  • Measure radius with a ruler
  • Time multiple oscillations for accuracy
  • Calculate velocity and plot force against $v^2$
• What does the graph of force against $v^2$ indicate?


  Should be a straight line through the origin
• How can we determine the mass of the bond from the graph?

  Gradient equals mass divided by radius
• What is the relationship between normal reaction and weight in circular motion at an angle?

  Normal reaction balances weight vertically
• How do we express the centripetal force in terms of normal reaction at an angle?

  $R \sin \theta =$$\frac{mv^2}{r}$
• What is the formula for tension in a conical pendulum?

  $T \cos \theta =$$mg$
• How do we find the speed in a system with two equations?

  Rearrange one equation for an unknown
• What is the formula for speed in terms of gravitational acceleration and angle?

  $v =$$\sqrt{g r \tan \theta}$
• What happens to forces in vertical circular motion at different positions?

  Forces act in the same or opposite directions
• How do we apply Newton's second law in vertical circular motion?

  Sum of forces equals mass times acceleration
• What is the normal contact force in position one of vertical circular motion?

  $R =$$\frac{mv^2}{r} +$$mg$
• What is the normal contact force in position two of vertical circular motion?

  $R =$$\frac{mv^2}{r} - mg$
• What are the key concepts in vertical circular motion?

  • Forces act in same or opposite directions
  • Normal force varies with position
  • Centripetal force is crucial for circular motion
  • Acceleration is centripetal at all points
• What should students do to ensure understanding of circular motion?

  Complete past paper questions
• What is the importance of this revision lesson?

  To understand circular motion concepts