Kinematics
This is defined as the distance moved in unit time.
speed
This law of Newton is based on equal reactions...
Newton's 3rd law
This is call the the turning effect of a force on a pivot ....
Moment of a force
Define mass of an object
The quantity of matter in an object
Joules is the unit of
Energy or work
Acceleration is defined as......
The rate of change of VELOCITY
Or
Change ( increase ) in a body's velocity in unit time
An example of newton's 3rd law is ....
A water sprinkler, person jumping off a boat , or a book resting on a table
The formula to calculate moments of a force =
Force x PERPENDICULAR distance of the force from the pivot .
State the units for mass and weights
Mass ,_ kilogram , weight ,_ newton
Power is defined as
The rate of doing work
Or
Work done / time taken
A car starts from rest , and reached a velocity of 15 m/s in 5s. What is the acceleration?
Acceleration = change in velocity / time taken
(15 - 0 ) / 5
= 3ms-2
State newton's 1st Law
A body in motion will continue to move with uniform velocity , or if at rest remains at rest ,
Unless an unbalanced force acts upon it
State the law of lever
When a body is in equilibrium the sum of the clockwise moments about one point
Equals the sum of the anticlockwise moments about that same point
State the definition for density and it's S.I units
Mass per unit volume . Kg/m3
A boy lifts 1 box of mass 3kg. What is the weight of the one box?
Weight= mass x gravity
= 3kg x 10 = 30 N.
Using speed , velocity, displacement, distance and acceleration.
Which 2 quantities are vector quantities ?
Which 2 quantities are scalar quantities ?
Scalar : size only = distance and sped
Vector : size and direction = displacement, velocity and acceleration
An 0.5kg egg is thrown at a speed of 8 m/s towards a wall, where it stuck and broke.
What is the Force the egg was thrown at , if it hit the wall in 1 second?
Force = change in momentum / time taken
= Mass x velocity change / time
= 0.5 (8-0) /1
= 4 N
What is the force that causes a moment of 2 Nm a distance of 20 cm from the pivot?
Moment = force x distance
Force = moment / distance
20Nm / 0.2 m. ( Recall 100 cm = 1m)
Force = 100 N
Calculate the density of an cube in kg/m3 for a mass 2400 g and length 2m?
Density = mass/ volume
2.4 kg / ( vol of cube = side 3 = 2 3)
2.4/8 = 0.3 kg/m3
If the boy takes 5 mins to lift 5 boxes a distance of 2m .what is his power ?
Work in moving 1 box = 30 N x 2m [ work = FxD]
Work moving 5 boxes = 30 x 2 x 5 = 300J
Power = work done / time
= 300 J / 300 s = 1 W
A car is moving at 20 m/s for 5 s, until a sudden brake is mashed and then car
Comes to a complete stop 4 seconds after.
Calculate the total distance during the entire time.
Total distance = distance when moving + distance when decelerating
Distance = speed x time
=( 20 x 5 ) + 1/2 ( 20x 4)
= 100+ 40 = 140m