12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
390 N
130 kg
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(a) Calculate the mechanical advantage of the lever that he is using.
(b) What type of lever is he using? Give a reason for your answer.
(c) If the force is applied 1 m from the pivot, calculate the maximumdistance between the
pivot and the load.
- A crowbar is used tolift a box of weight 400N. The box is placed 75cm from the pivot. A crow
bar is a class 1 lever.
(a) Why is a crowbar aclass 1 lever? Draw a diagram to explain your answer.
(b) What force F needsto be applied at a distance of 1,25 m from thepivot to balance the
crowbar?
(c) If force F was applied at a distance of 2 m, what would the magnitude of F be?
- A wheelbarrow is used to carry a load of 200N. The load is 40 cm from the pivot and the force
F is applied at a distanceof 1,2 m from the pivot.
(a) What type of lever isa wheelbarrow?
(b) Calculate the force Fthat needs to be appliedto lift the load.
- The bolts holding acar wheel in place is tightened to a torque of90 N· m. The mechanic
has two spanners to undo the bolts, one witha length of 20 cm andone with a length of 30
cm. Which spanner should he use? Give a reason for your answer by showing calculations and
explaining them.
More practice video solutions or help at http://www.everythingscience.co.za
(1.) 01xb (2.) 01xc (3.) 01xd (4.) 01xe (5.) 01xf (6.) 01xg
Chapter 12 — Summary
See the summary presentation ( Presentation: VPkkv at http://www.everythingscience.co.za)
Newton’s First Law Every object will remain at rest or in uniform motion in a straight line unless it is
made to change its stateby the action of an unbalanced force.
Newton’s Second Law The resultant force acting on a body will cause the body to acceleratein the
direction of the resultant force The accelerationof the body is directly proportional to the mag-
nitude of the resultant force and inversely proportional to the mass of theobject.
Newton’s Third Law If body A exerts a forceon body B then body Bwill exert an equal but opposite
force on body A.
Newton’s Law of Universal Gravitation Every body in the universe exerts a force on every other body.
The force is directly proportional to the productof the masses of the bodies and inversely pro-
portional to the square of the distance between them.
