Multiple Choice
A 500 kg car is parked on a hill with a 5° slope. What is the magnitude of the friction force acting on the car to prevent it from sliding down?
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6. Intro to Forces (Dynamics)
Forces & Kinematics
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An object moves along a straight line and is at position A, where its velocity is decreasing in the positive -direction. What is the direction of the net force acting on the object at position A?
A
In the negative -direction
B
In the positive -direction
C
Perpendicular to the -direction
D
There is no net force acting on the object
Verified step by step guidance1
Recall Newton's Second Law, which states that the net force acting on an object is related to its acceleration by the equation \(\mathbf{F}_{net} = m \mathbf{a}\), where \(m\) is the mass and \(\mathbf{a}\) is the acceleration vector.
Understand that acceleration is the rate of change of velocity. Since the velocity is decreasing in the positive \(x\)-direction, the acceleration must be directed opposite to the velocity vector.
Because the velocity is along the positive \(x\)-direction and is decreasing, the acceleration points in the negative \(x\)-direction.
Since the net force is in the same direction as the acceleration, the net force must also be directed in the negative \(x\)-direction.
Therefore, the direction of the net force acting on the object at position A is opposite to the direction of the velocity, which is the negative \(x\)-direction.
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