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Physics - Practice Problems

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1. A ball with a mass of 200 g is whirled in a circle at the end of a string 100cm long whose breaking strength is 100 N. neglecting gravity, the maximum speed of the ball is approximately.
2m/s
7m/s
10m/s
50m/s

2.A 1-kg object is moving at 10m/s. To double its kinetic energy, its speed should be increased to approximately.
14m/s
15m/s
20m/s
40m/s

3.A 430-g soccer ball lying on the ground is kicked with a force of 800N. If the kick lasts 0.01 s, the ball flies off with a speed of.
0.0186 m/s
0.182 m/s
1.90 m/s
18.6 m/s

4. The speed of a 4000-kg truck whose KE is 1.8 MJ is
0.95m/s
30m/s
94m/s
900m/s

5.the 2.5-kg head of an ax exerts a force of 80kN as it penetrates 18mm into the truck of a tree. the speed of the ax head when it strikes the tree is.
1.2m/s
3.4m/s
34m/s
107m/s

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https://brainmass.com/physics/classical-mechanics/physics-practice-problems-189414

Solution Preview

(1) Tension force = Centripetal force = m v^2 /r

100 = 0.2 * v^2 / 1

v^2 = 100/0.2 = 500

v = sqrt 500 = 22.36 m/s is the maximum speed

(None of the options match. Please check again at your end.)

(2) Since KE ...

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