An object is moving along the ground in a straight line at a constant speed.
Which statement about the resultant force acting on the object is correct?
A The resultant force acting on the object is equal to its weight.
B The resultant force acting on the object is equal to the product of its mass and its velocity.
C The resultant force acting on the object is equal to the resistive force.
D The resultant force acting on the object is equal to zero.
ANSWER: D
The Physics Behind
- Newton's 2nd Law of Motion [or the Law of Acceleration] states that an object's acceleration is directly proportional to the resultant force on it when mass is unchanged.
- A movement along a straight line at constant speed means that the acceleration is zero.
- Therefore, by virtue of the 2nd Law, resultant force on the object must also be zero.
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