1. A particle undergoing circular motion in the xy-plane stops on the positive y-axis.
Which of the following does not describe its angular position?
A. -3/2πrad
B. 1/3πrad
C. 5/2πrad
D. 1/2πrad
2. Suppose a bolt on your car engine needs to be tightened to a torque of 15 N⋅m . You are using a 10-cm-long wrench, and you apply a force at the very end in the direction that produces maximum torque.
What force should you apply?
A. 1500 N
B. 300 N
C. 150 N
D. 30 N
3. A car traveling at a steady 20 m/s has 74 cm -cm-diameter tires
What is the approximate acceleration of a piece of the tread on any of the tires?
A. 32 m/s^2
B. 11 m/s^2
C. 1100 m/s^2
D. 3200 m/s^2
Physics Easy 10 points ?
2016-07-16 4:52 am
回答 (2)
2016-07-16 5:45 am
✔ 最佳答案
i) ⅓π cause its(⅓180°) 60° counter clockwise from +tive x-axis.all the others are 90°. option B
ii) moment of a force = torque = τ = force x perpendicular distance = F x (0.1) = 15 Nm
=> F = 15/0.1 = 150 Newtons. option C
iii) v = rω, d = 2r
=> ω = v/r = 20 / 0.37 = 54.054 rad/s
therefore centripetal acceleration = a = ω²r = v²/r = 54.054²(0.37) = 1081.081 m/s² ~= 1100 m/s² (ii s.f) Ans: option C
hope this helps
2016-07-16 5:38 am
1)
B , i.e. π/3
2)
F = T/ℓ = 15/0.1 = 150 N
3)
ac = V^2/r = 20^2/0.37 = 1080 m/sec^2 ...rounded up 1100 m/sec^2
B , i.e. π/3
2)
F = T/ℓ = 15/0.1 = 150 N
3)
ac = V^2/r = 20^2/0.37 = 1080 m/sec^2 ...rounded up 1100 m/sec^2
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