How many forces act on an object that is moving at constant speed?

• A. Two
• B. Four
• C. One
• D. Zero

Answer: (B)

When an object moves at constant speed, its velocity isn’t changing, so its acceleration is zero. That means the total, or net, force acting on it must be zero. But that doesn’t mean there are no forces at all. There can be several forces present as long as their effects cancel out.

A common setup is four forces: weight pulling downward, the normal force from the surface pushing upward, friction opposing the motion, and an applied force pushing forward. If the forward push balances the friction and the weight is balanced by the normal force, the sum of all forces is zero, so the object keeps moving at the same speed. So four forces can be present and still result in zero net force, which aligns with constant speed.

Remember, the exact number of forces isn’t fixed—the key idea is that their combined effect is zero.