A 5 kg object slides on a rough table with
coefficient of kinetic friction µk = 0.1. The
initial velocity of the object is 2 m/s. Find
(a) the initial kinetic energy of the object
A.
B.
C.
D.
E.
2 joules
5 joules
10 joules
20 joules
50 joules
KE = ½ m v2
= ½ (5) (2)2
= 10 J
A 5 kg object slides on a rough table with
coefficient of kinetic friction µk = 0.1. The
initial velocity of the object is 2 m/s. Find
(a) the initial kinetic energy of the object,
and (b) the distance it travels before
coming to rest. (use g = 10 m/s2)
A.
B.
C.
D.
E.
Friction fk = µk n = µk mg
1 meter
= 0.1 (5)(10) = 5 N
2 meters
Wnet = KEf − KEi = ∆KE
5 meters
10 meters
F(∆x)cos θ = 0 – 10 J
20 meters
5(∆x)(-1) = 0 – 10 J
Quiz (will count for credit)
Problem 5.46 (modified) A child of mass m starts from rest and
slides without friction from a height h along a curved
waterslide. She is launched from a height h/5 into the pool.
Define the gravitational potential energy to be zero on ground
level. (a) Find her potential energy and kinetic energy at the
top of the waterslide.
A.
B.
C.
D.
E.
h
d
PE
PE
PE
PE
PE
=
=
=
=
=
mgh, KE = 0
0, KE = mgh
mgh, KE = mgh
mgd, KE = -mgh
mgd, KE = 0