Chapter 2 – 2a. Ticker Tape

1. Ticks and Dots The dots are the marks made on the ticker tape by the ticker tape time. A tick is the time taken to make 2 consequences dots. Remember! A tick is a time. It is not the distance between 2 dots.

1 thick Dots

Time taken to make 2 subsequent dots is called 1 tick.

2. How to analyse ticker tape----- Important to know! When the dots are close to each other, the velocity is low. When the dots are further from each other, the velocity is high.

3. Analysing motion from ticker tapes

The figure shows the distribution of the dots for : I. Uniform velocity

II. Decreasing velocityIII. Increasing velocity

4. Analysing motion from ticker tape charts

5. Finding time from a ticker tape----- Must know!

1 tick = 0.02s(For a ticker tape timer of frequency 50Hz)

6. Finding Velocity from Ticker Tape----- Must know! The velocity of a motion can be determined by using the equation v=s/t, as

shown in the figure below.

7. Finding Acceleration from Ticker Tape----- Must know! The acceleration of a motion can be determined by using the equation.

8. Example – Finding Acceleration from Ticker Tape

9. Example – Finding Acceleration from Ticker Tape Chart

Chapter 2 – 2b. Effects of Force

5 4 7

9 1 2 8 3 6 10

1. Crumble Zoon The crumble zone increases the reaction time of collision during an accident.

This causes the impulsive force to be reduced and hence reduces the risk of injuries.

2. Seat Belt Seat belt prevent the driver and passengers from being flung forward or

thrown out of the car during an emergency brake.3. Airbag

The inflated airbag during an accident acts as a cushion to lessen the impact when the driver flings forward hitting the steering wheel or dashboard.

4. Padded Dashboard Dashboard covered with soft material. This may increase the reaction time

and hence reduce the impulsive force when passenger knocking on it in an accident.

5. Windscreen Shatter – proof glass is used as windscreen of a car so that it will not break

into small pieces when broken. This may reduce injuries caused by scattered glass.

6. Head Rest Reduce neck injury when driver and passengers are thrown backwards when

the car is banged from backward. 7. Collapsible Steering Columns

The steering will swing away from driver’s chest during collision. This may reduce the impulsive force acting on the driver.

8. Anti – lock braking System (ABS) Prevent the wheels from locking when brake applied suddenly by adjusting

the pressure of the brake fluid. This can prevents the car from skidding.

9. Bumper Made of elastic material so that it can increases the reaction time and hence

reduces the impulsive force caused by collision. 10. Passengers Safety Cell

The body of the car is made from strong, rigid steel cage. This may prevent the car from collapsing on the passengers during a car

crash. Chapter 2 – 2c. Work, Energy, Power and Elasticity

1. Work Done ----- Must Know! Work done by a constant force is given by the product of the force and the

distant moved in the direction of the force. In mathematics, we write :

Work = Force x Displacement x cos θ

2. Unit of Work ----- Must know! The SI unit of work is Joule (J)

1 J = 1 NM3. Work done 2 ----- Must Know!

If the direction of force is equal to the direction of motion, wirk done can be calculated by using the following equation : W = F x s W = Work; F = Force; s = Displacement

4. Work done by gravity ----- Must know! Work done by gravity can be calculated by using the equation :

W = mgh W = Work m = Mass of object g = gravitational field strength h = vertical distance of the object

5. Work done against gravity Work done against gravity can also calculated by using the equation :

W = mgh W = Work M = Mass of object g = gravitational field strength

6. Summary

7. Finding Work Done from force-Distance Graph------must know!

In a Force-Distance Graph, work done is equal to the are between the graph and x-axis.