28/02/2019 Dog-nap

Unscramble the note left at the scene of the crime 28/02/2019 Unscramble the note left at the scene of the crime ‘ YOU NOT BY JERRY HAVE SEE IF ME YOUR SPRINGER NEVER WILL DOG £9,999 TOMORROW GIVE I DO AGAIN YOU ’

28/02/2019 Levers Levers are simple machines. They can make work easier by increasing the size of a force. Forces can move objects by turning them around a point, we call this a pivot. A seesaw is a lever, when you push down on one side you are applying an effort, and the person on the other side (the load) moves up. Label the diagram

Levers 28/02/2019 Pivot Effort Load

A force acting on an object can cause it to turn about a pivot. 28/02/2019 pivot 5N A force acting on an object can cause it to turn about a pivot. What would happen to the see-saw above ? Would it turn? If so, clockwise or anti-clockwise?

The turning effect of a force is called a moment. 28/02/2019 pivot The left goes down - an anticlockwise turn. The turning effect of a force is called a moment. We use many simple levers in the home Write down three examples of levers

Moments Pivot Distance from force to pivot Force 28/02/2019 Pivot Distance from force to pivot Force Suppose you were trying to unscrew a nut using a spanner. The spanner exerts a moment or turning force on the nut. If the moment is big enough it will unscrew the nut. If not there are 2 ways of increasing the moment.

Increasing the moment 28/02/2019 1. Increase the distance from the force to the pivot - apply the force at the end or use a longer spanner. Pivot Distance from force to pivot Force

Increasing the moment 28/02/2019 2. Increase the force applied - push/pull harder or get someone stronger to do it! pivot Distance from force to pivot Force

F x d Moment The moment of a force is given by the relationship: 28/02/2019 The moment of a force is given by the relationship: Moment = Force (N) x Distance (cm or m). Moments are measured in Newton centimetre (Ncm) or Newton metre (Nm). moment F x d

Moments calculation 28/02/2019 Gina weighs 500 N and stands on one end of a seesaw. She is 0.5 m from the pivot. What moment does she exert? moment = 500 x 0.5 = 250 Nm 0.5 m 500 N pivot

Moments F x d moment Calculate the following turning moments: 5 metres 28/02/2019 moment Calculate the following turning moments: F x d 5 metres 100 Newtons 2 metres 200 Newtons

Objects found near the scene of the crime 28/02/2019 Objects found near the scene of the crime Crowbar 40cm Letter opener 17cm Spanner 29cm Screwdriver 24cm

Results Crowbar 40cm x 80N = 3200N/cm 28/02/2019 Crowbar 40cm x 80N = 3200N/cm Letter opener 17cm x 80N = 1360N/cm Spanner 29cm x 80N = 2320N/cm Screwdriver 24cm x 80N = 1920N/cm Therefore only the crow bar and spanner could have been used to lever open the window

Further results Force = Moment ÷ Distance Letter opener 28/02/2019 Further results Force = Moment ÷ Distance Letter opener 2000N/cm ÷ 17cm = 118N Screwdriver 2000N/cm ÷ 24cm = 83N

Further results When you double the force applied… Letter opener 28/02/2019 When you double the force applied… Letter opener 17cm x 160N = 2720N/cm Screw driver 24cm x 160N = 3840N/cm Therefore the letter opener and screw driver may have been used if there were two people applying force