# Physics: Kinematics

Mechanics

Nov 14, 2013 (4 years and 5 months ago)

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Physics:
Kinematics

Andy
Onorato

Kinematics equation 1

Kinematics equation 2

Kinematics equation 3

Force of Gravity

Normal Force

Force Equation

Tension Force

Frictional Force

Kinematics Equation 1

The first kinematics equation is v = v
0

+ at.

This equations states that the speed of an object can be
determined by first multiplying the acceleration by how
long the object is traveling and then adding that speed
to the initial speed of the object.

Example: A car that starts at rest accelerates uniformly for 5
sec at 3m/s
2
, how fast is the car going after that 5 sec?

v
= v
0

+
at

v = 0 + (3)(5)

v = 15m/s

Kinematics Equation
2

The second kinematics equation is v
2

= v
0
2

+ 2ax.

This equations states that the speed squared of an object
can be determined by first multiplying the acceleration
and the distance traveled of an object by 2, and then
adding that speed to the initial speed squared of the
object.

Example: A boy is standing on the top of the bleachers with a
super ball. He throws the ball straight at the ground at an initial
speed of 5m/s. The bleachers are 30m tall and the acceleration
due to gravity is 10m/s
2
. At what speed does the ball strike the
ground?

v
2

= v
0
2

+
2ax

v
2

=
(5)
2

+
2(10)(30)

v
2

=
625m/s

v = 25m/s

Kinematics Equation
3

The third kinematics equation is x = v
0
t + ½at
2
.

This equations states that the distance an object travels
can be determined by first multiplying the initial speed
by how long the object travels at that speed. Then add
that amount to ½ the acceleration multiplied by the time
squared.

Example: A girl is jogging at a constant speed of 2m/s. For 6
sec she accelerates at a rate of 1 m/s
2
. How far does she travel
during her time of acceleration.

x
= v
0
t + ½
at
2

x = (2)(6) + ½(1)(6)
2

x = 12 + 18

x = 30m

Force Equation

The equation we can use to find the force is Force equals the
mass multiplied by the acceleration. So if a 400g object is
accelerating at a constant of 5m/s
2
, how much force does the
object have?

F = ma

Force of Gravity

The force of gravity is the amount of force the object feels
from gravity. It can be found by multiplying the mass times
the acceleration due to gravity (9.8m/s
2
)

F
g

= mg

Normal Force

the
normal force

(F
N
)

is the component, that keeps an object
from pushing through another
surface. For
example,

the surface
of a floor or wall, preventing the object from penetrating the
surface.

Tension Force

The tension
is the pulling force exerted by a string, cable,
chain,
etc

on
another
object.

Frictional Force

Friction is the
force resisting
the relative motion of solid surfaces, fluid layers,
and material elements sliding against each other.

How fast does a ball hit
the ground when dropped
from a 20m building?

392 m/s
2

19.8 m/s

10 m/s
2

50 m/s
2

Congratulations!!

problem

Hang in there.

You can do it!

problem

Complete the problem and then

Physics Problem

Note that the tension force

on each of the blocks is
of the same magnitude. If

the large block (5g)
feels a force of 10 N,
and the small block weighs
3 g, What force is exerted on the smaller block?

Large Block

F = ma

10 = (5)a

a = 2 m/s
2

Small Block

F = ma

F = (3)(2)

F = 6 N

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