Ex 2) A 10 kg
frictionless cart is resting on a horizontal table. A force of 10 N is
applied to the cart for a distance of 8 m. What is the carts new KE?

Ex 2) A 10 kg
frictionless cart is resting on a horizontal table. A
force of 10 N is applied to the cart for a distance of
8 m. What is the carts new
kinetic energy?

m = 10 kg

F = 10 N

d = 8 m

KE = (˝)mv^{2 }??

ΔKE
=
W

= Fd = 10N(8m)

= 80 Nm

Ex 3) 100
Joules of work is needed to lift a 100 kg object from the ground.

What is the objects new P.E.?

Ex 3)100
Joules of work is needed to
lift a 100 kg
object from the ground.

What is the objects new
P.E. ?

W = ΔPE
= 100J

Ex 4) Crate
is pulled 6.00 m up an incline with a force of 50.0 N. P.E. of cart
increases by 250. J.

Total work done
against friction?

Ex 4) Crate is pulled 6.00 m up an incline
with a force of 50.0 N.
If the PE of
the cart increases by 250. J.
, what is the total work done against
friction?

d = 6.00 m

F = 50.0 N

ΔPE = 250. J

W = Fd = 50.0 N(6 m)

= 300. J

W = ΔPE + W_{f}

300. J = 250. J + W_{f}

W_{f} = 50.0 J

Ex 5) 4
N is exerted on a 1 kg mass at rest for 2 m, causing it to move

A.
Find the objects
K.E.

KE = (1/2)mv^{2}

Work on object = ΔKE

ΔKE = W = Fd = 4 N(2 m)

= 8 Nm

B. Find the
objects velocity

KE = (1/2)mv^{2}

8 Nm = (1/2)1 kg(v^{2})

16 =
v^{2}

^{V = 4 m/s}

Ex 6) A force of
100.0 N lifts the object 10.00 m off the ground. What is the object's
new PE?

What is the mass of the object?

Ex 6) A force
of 100.0 N lifts the object
10.00 m off the ground. What is the
object's new potential energy?

mass of object?

ΔPE = W = Fd

=
100.0 N(10.00 m)

= 1000. Nm

What is the mass of the object?

PE = 1000. J = mgh

= m(9.8 m/s^{2})10.00
m = 1000. J

m = 10.20 kg

Ex 7) Spring
has a spring constant of 2.0 N/m.

How much work must be done to stretch
5.0 m from its equilibrium position?

Ex 7) A spring
has a spring constant of 2.0 N/m. How
much work
must be done to stretch it 5.0 m
from its equilibrium position?

k = 2.0 N/m

x = 5.0 m

W = ?

W = PE = 1/2kx^{2 }

^{ }

= (1/2)2.0 N/m(5.0 m)^{2}

= 25. J

Ranking
Task

Rank the KE of the car from largest to
smallest

B, C, D, A

How much farther will
a car traveling at 100 km/s skid than the same car traveling
at 50 km/s?

A) 4X as far B) 2 X as far
C) The same distance
D) 5X as far
E) 1/2 as far

Review

Name the energy conversion that
occurs in a Grandfather clock.