Question

which of the following are examples of a balanced force? a dog sitting still. a boat turning around. playing a game of tug of war. hitting a tennis ball. a car moving at a constant speed and direction.

Explanation:

• When a dog is sitting still, the force of gravity pulling it down and the normal force from the ground pushing it up are equal in magnitude and opposite in direction. So, the net force is zero, which is an example of balanced forces.
• For a car moving at a constant speed and direction, the force of the engine (thrust) and the resistive forces (like air resistance and friction) are balanced. The net force is zero as there is no acceleration.
• In a game of tug - of - war, if the two teams are pulling with equal force, the forces are balanced. But the option just says "playing a game of tug of war" which is a bit ambiguous. However, conceptually, when the forces are equal (a common scenario in a'static' tug - of - war moment), it's balanced.
• A boat turning around is changing its direction, so there is an acceleration (centripetal acceleration in case of circular - like turning). According to Newton's second law \(F = ma\), if there is acceleration (\(a

eq0\)), the net force (\(F\)) is not zero. So, forces are unbalanced.

• Hitting a tennis ball changes the ball's velocity (either speed, direction, or both). Since there is a change in velocity, there is an acceleration. By Newton's second law, the net force is not zero, so forces are unbalanced.

Answer:

A. A dog sitting still.
C. Playing a game of tug of war (when forces are equal).
E. A car moving at a constant speed and direction.