Why do we use cos 0 degrees when we calculate external force?

College Physics
11th Edition
ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter1: Units, Trigonometry. And Vectors
Section: Chapter Questions
Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...
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Why do we use cos 0 degrees when we calculate external force?

17. A box with a mass of 25 kg is tied to a rope and pulled up a ramp (the rope is
parallel to the ramp); the tension in the rope is 90 N, and the force of kinetic friction
between the box and ramp has a magnitude of 20 N. The ramp is 6.0 m long, and the
angle it makes with the horizontal is 15°. If the box started at rest at the base of the
ramp, what is its kinetic energy at the top of the ramp?
rope
As
f
sin 1591
ch
A) 40 J
B) 280 J
C) 1100J
D) 420 J
L = 6.0 m
E) 160 J
15°
+
Conserve Energy for
box,
Earth
гамр
I is an external force
Wext = W₂₁ = T • A ²
_sef ly = 0
U;
+ K₂
0 + 0 + TL
11
= TL cos pº
=TL
M÷0 so AE = L
f₁
Wext = Us + K + DE ₁h
mg h + ke + f₂L
Ke
=
Transcribed Image Text:17. A box with a mass of 25 kg is tied to a rope and pulled up a ramp (the rope is parallel to the ramp); the tension in the rope is 90 N, and the force of kinetic friction between the box and ramp has a magnitude of 20 N. The ramp is 6.0 m long, and the angle it makes with the horizontal is 15°. If the box started at rest at the base of the ramp, what is its kinetic energy at the top of the ramp? rope As f sin 1591 ch A) 40 J B) 280 J C) 1100J D) 420 J L = 6.0 m E) 160 J 15° + Conserve Energy for box, Earth гамр I is an external force Wext = W₂₁ = T • A ² _sef ly = 0 U; + K₂ 0 + 0 + TL 11 = TL cos pº =TL M÷0 so AE = L f₁ Wext = Us + K + DE ₁h mg h + ke + f₂L Ke =
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