Which of the following would cause a fan cart to accelerate the least? - doubling the speed of the fan
- pointing the fan exhaust downward
- tripling the speed of the fan
- pointing the fan exhaust upward

The correct option is;

-Pointing the fan exhaust upward

Explanation:

The fan cart transfers reaction force from the jet of air it blows through the exhaust into motion in the opposite direction of the jet. By pointing the fan exhaust upwards, the direction of motion of the cart is therefore, into the ground. Due to the solid nature of the ground the motion is resisted, and by Newton's first law of motion, a body will remain in motion unless resisted by a force. In the case of the question, the ground is resisting the motion of the cart and the cart will remain at rest and having zero acceleration.

terd muffin is the correct answer