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Question 1:
What is the magnitude of the vector 3A - B in the figure above?
A.3 B.4 C.5 D.2 E.6
Question 2:
The graph above shows the acceleration of a particle. At t = 0s, the speed of the particle is 1m/s. What is the speed of the particle at t = 4s?
11 m/s
9 m/s
19 m/s
13 m/s
10 m/s
Question 3:
Forces F1 and F2 in the figure above act on a block of mass m = 10kg that moves on a frictionless surface. What is the acceleration of the block?
1 m/s
1.5 m/s
2 m/s
2.5 m/s
3 m/s
Question 4:
A block of mass m is moving down an inclined plane with a decreasing speed. The coefficient of friction between the block and the plane is μ. Which of the following statements is true?
sin(α) < μ
sin(α) > μ
cos(α) < μ
cos(α) > μ
tan(α) < μ
Question 5:
When a car's kinetic energy increases 9 times, what happens with its speed?
increases 9 times
increases 3 times
decreases 9 times
decreases 3 times
remains constant
Question 6:
An object of mass 4kg is attached to a spring. The equilibrium position of the object is .4m from the point where the spring exerts no force on the object. What is the spring constant, k?
10 N/m
80 N/m
100 N/m
150 N/m
200 N/m
Question 7:
An object of mass 10kg sitting on a frictionless horizontal plane is moved from a stationary state by the force shown above. What is the velocity of the object at time t = 5s?
2.5 m/s
3 m/s
4 m/s
5 m/s
6 m/s
SAT2物理练习题参考答案与解析参见下一页
Question 1:What is the magnitude of the vector 3A - B in the figure above?
Solution:
The magnitude of the vector 3A is 3 and the magnitude of vector B is 4. The angle between vectors 3A and B is 90o. According to the Pythagorean theorem, the magnitude of 3A - B is 5.
Question 2:
The graph above shows the acceleration of a particle. At t = 0s, the speed of the particle is 1m/s. What is the speed of the particle at t = 4s?
Solution: At t = 2s, the speed of the particle is v2s = v0s + 2m/s2·2s = 5m/s.
At t = 4s, the speed of the particle is v4s = v2s + 3m/s2·2s = 11m/s.
Question 3:
Forces F1 and F2 in the figure above act on a block of mass m = 10kg that moves on a frictionless surface. What is the acceleration of the block?
Solution: F1cos(60o) + F2cos(60o) = m·a
20·1/2 + 30·1/2 = 10·a
25 = 10·a
a = 2.5m/s2
Question 4:
A block of mass m is moving down an inclined plane with a decreasing speed. The coefficient of friction between the block and the plane is μ. Which of the following statements is true?
Solution: mg sin(α) - � mg cos(α) = a
The speed is decreasing so a < 0. This means that
mg sin(α) - � mg cos(α) < 0
mg sin(α) < � mg cos(α)
tan(α) < �
Question 5:
When a car's kinetic energy increases 9 times, what hapens with its speed?
Solution: The car's initial kinetic energy is Ei = mvi2/2 and the final kinetic energy is Ef = mvf2/2.
Ef/Ei = (vf/vi)2
(vf/vi)2 = 9
vf/vi = 3
Question 6:
An object of mass 4kg is attached to a spring. The equilibrium position of the object is .4m from the point where the spring exerts no force on the object. What is the spring constant, k?
Solution:
F = kx
mg = kx
k = mg/x
k = 40N/.4m
k = 100N/m
Question 7:
An object of mass 10kg sitting on a frictionless horizontal plane is moved from a stationary state by the force shown above. what is the velocity of the object at time t = 5s?
Solution: The area under a force versus time graph gives us the impulse given to the object.
p = 10/2 + 30 + 10/2 = 40 kg m/s
v = p/m
v = 4 m/s
