Phys101
Term:123
Online HW-Ch08-Lec02
Q1:
A Block of mass m = 5.00 kg is released form rest from point A and slides on the
frictionless track shown in figure. Determine the block’s speed at points B and C:
A.
B.
C.
D.
E.
vB
vB
vB
vB
vB
= 5.94 m/s, v c = 7.67 m/s
= 2.14 m/s, v c = 1.62 m/s
= 1.84 m/s, v c = 3.47 m/s
= 9.19 m/s, v c = 10.0 m/s
= 9.19 m/s, v c = 15.0 m/s
Ans:
A;
1
2
mvB 2 + mgyB =
1
2
mvA 2 + mgyA
⇒ vB = �vA 2 + 2g(yA − yB )
= 5.94 m/s
vc = �vA 2 + 2g(yA − yC ) = 7.67 m/s
Q2:
In Figure, a 3.5 kg block is accelerated from rest by compressed spring of spring
constant 640 N/m. The block leaves the spring at the spring’s relaxed length and then
travels over horizontal floor with a coefficient of kinetic friction u k = 0.25. The
frictional force stops the block in distance D = 7.8 m. What is the original
compression distance of the spring?
Ans:
∆K + ∆U + ∆E+n = 0
1
(k f − k i ) + (Uf − Ui ) + µk mgD − kx 2 + +µk mgD = 0
2
2µk mgd
⇒x= �
= 0.46 m
k
KFUPM-Physics Department
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Phys101
Q3:
Term:123
Online HW-Ch08-Lec02
A 4.0 kg bundle starts up a 30ᵒ incline with 128 J of kinetic energy. How far will it
slide up the incline if the coefficient of kinetic friction between bundle and incline is
0.30?
Ans:
∆K + ∆U + ∆E+n = 0
(k f − k i ) + (Uf − Ui ) + µk mgcosθd = 0
−k i + Uf + µk mgcosθd = 0
−k i + mgh + µk mgcosθd = 0
−k i + mgdsinθ + µk mgcosθd = 0
⇒d=
h
30ᵒ
h = d sinθ
ki
= 4.3 m
mg(sinθ + µk cosθ)
KFUPM-Physics Department
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