Question

which of the following describes an object with a non - zero net force acting on it?
the spaceship traveled at a constant speed in a straight line.
the car drove 65 mph while moving in a straight line.
the motorcycle traveled at a constant velocity.
the truck traveled at a constant speed while making a right turn.
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1. - / 1 points

which of the following describes an object with zero net force acting on it?
the truck slowed down while making a right turn.
the spaceship traveled at a constant speed in a straight line.
the motorcycle traveled at a constant speed while making a u - turn.
the car sped up from 50 mph to 65 mph while moving in a straight line. the moped accelerated while making a left turn.

Explanation:

According to Newton's first law, if an object is in a state of uniform motion in a straight line (constant velocity, which means both constant speed and constant direction), the net force acting on it is zero. When an object changes its direction (even if speed is constant) or changes its speed, there is a non - zero net force.

• For the first question:
• The spaceship traveling at a constant speed in a straight line has constant velocity (zero net force).
• The car driving at 65 mph in a straight line (assuming constant speed) has constant velocity (zero net force if speed is truly constant).
• The motorcycle at constant velocity has zero net force.
• The truck making a right - turn (even at constant speed) changes direction. Since velocity is a vector (has both magnitude and direction), a change in direction means a change in velocity. According to \(F = ma\) (where \(a=\frac{\Delta v}{\Delta t}\)), a non - zero acceleration (\(a\)) implies a non - zero net force (\(F\)).
• For the second question:
• The truck slowing down while turning has a change in speed and direction (non - zero acceleration, non - zero net force).
• The spaceship traveling at a constant speed in a straight line has constant velocity (zero net force).
• The motorcycle making a U - turn (even at constant speed) changes direction (non - zero acceleration, non - zero net force).
• The car speeding up in a straight line has a change in speed (non - zero acceleration, non - zero net force). The moped accelerating while turning has a non - zero acceleration (non - zero net force).

Answer:

For the first question: The truck traveled at a constant speed while making a right turn.
For the second question: The spaceship traveled at a constant speed in a straight line.