Cette leçon contient 23 diapositives, avec diapositives de texte et 2 vidéos.
La durée de la leçon est: 45 min
Éléments de cette leçon
Force and motion
Slide 1 - Diapositive
This lesson
Recap
free fall
acceleration due to gravity
studying
Slide 2 - Diapositive
Newtons First law of motion
Newtons second law of motion
Slide 3 - Diapositive
Newtons first law — Inertia
Newtons second law
Slide 4 - Diapositive
Newtons first law — Inertia
An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.
Newtons second law
Slide 5 - Diapositive
Newtons first law — Inertia
An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.
Newtons second law
Fres=m⋅a
Slide 6 - Diapositive
Newtons first law — Inertia
An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.
Newtons second law
Fres=m⋅a
[1N]=[1kg]⋅[s2m]
Slide 7 - Diapositive
Inertia
The property of mass that it resists changing speed
Slide 8 - Diapositive
Free Fall
Acceleration due to gravity
Slide 9 - Diapositive
Slide 10 - Vidéo
Slide 11 - Diapositive
Falling in the air
A v-t diagram of a skydiver jumping out of a plane
Slide 12 - Diapositive
Slide 13 - Vidéo
4.3 Force and work
Slide 14 - Diapositive
work
Forces cause objects to accelerate (change speed).
Changing in speed means an object gains or looses kinetic energy (movement energy)
Work is a measure of how much kinetic energy a force transfers to an object.
Slide 15 - Diapositive
Work
W: the work that the force has carried out (the amount of kinetic energy a force has transferred to an object).
F: The magnitude of the force acting out the work.
S: The distance this work caused the object to move.
W=F⋅s
Slide 16 - Diapositive
Work
W: the work that the force has carried out (the amount of kinetic energy a force has transferred to an object).
F: The magnitude of the force acting out the work.
S: The distance this work caused the object to move.
W=F⋅s
A force that causes an object to move is called a motive force
Slide 17 - Diapositive
Work
W=F⋅s
Quantity
Unit
Work (W)
Newton-meter (Nm)
Force (F)
Newton
Distance covered (s)
meter
Slide 18 - Diapositive
Practice problem
Jane and Wendy are going on holiday. They attach their caravan to the car and drive to the campsite, 50 km away (figure 2). The car exerts a pulling force of 1.2 kN on the caravan.
Calculate the work done on the caravan.
Slide 19 - Diapositive
Work and energy
work is related to energy.
1 Newton-meter of work = 1 joule of energy
When considering for example a carengine, the work done by the car comes from the useful energy supplied by the engine.
Slide 20 - Diapositive
Work and energy
η=EtotEused⋅100
Eused=work
Slide 21 - Diapositive
Practice problem
Dimah uses the setup in figure 4 to determine the efficiency of a small electric motor. The motor takes 6.0 s to pull the wood block 1.8 m. During those 6.0 s, the voltmeter reads 1.5 V and the ammeter 0.64 A. The tractive force acting on the wood block is 2.5 N.
La durée de la leçon est: 45 min
