Question

lo: swbat investigate the effects of balanced and unbalanced forces on an objects state of motion and use newtons first law of motion to analyze these effects.
dol: given a set of problems, students will investigate the effects of balanced and unbalanced forces on an objects state of motion and use newtons first law of motion to analyze these effects, by answering at least 4 of 5 questions correctly.
1 maya is driving her friends to a science museum in her car.
maya suddenly applies the brakes. how does this affect an unrestrained passengers motion, according to newtons first law?
a. the passenger immediately changes their state of motion to match the cars.
b. the passenger maintains their original state of motion relative to the ground.
c. the passenger continues their forward motion relative to the car due to inertia.
d. the passenger moves backward relative to the car due to the braking force.
2 read the scenario below and answer question #2.
a soccer player kicks a stationary ball across the field. later, the player stops the ball with their foot. what does this demonstrate about the forces acting on the ball?
a. the player is applying an unbalanced force to change the balls state of motion.
b. the forces on the ball are balanced, so it will not move.
c. the players action will have no effect on the ball.
d. the ball will instantly stop on its own due to friction.

Explanation:

1. According to Newton's First Law (Law of Inertia), an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. When the car suddenly stops (due to braking force on the car), the unrestrained passenger (who is not directly acted on by the braking force) has inertia - they maintain their original state of motion (which was the motion of the car before braking) relative to the ground. Option A is wrong because the passenger doesn't immediately match the car's new (stopped) state. Option C is incorrect as the passenger moves forward relative to the car (not backward). Option D is wrong as there is no backward - acting force on the passenger from braking (the braking force acts on the car).
2. When the soccer player kicks the stationary ball, the ball starts moving, and when the player stops the ball, its state of motion changes (from moving to stationary). An unbalanced force (the force from the player's foot in both cases - kicking to start motion and stopping to end motion) is required to change the ball's state of motion (from rest to motion and vice - versa). Option B is wrong because if forces were balanced, the ball would either stay at rest (if initially at rest) or move at a constant velocity (if already in motion). Option C is incorrect as the player's action clearly has an effect. Option D is wrong because friction would act over time to slow the ball, but the player's direct force is what stops it immediately in this context.

Answer:

1. B. The passenger maintains their original state of motion relative to the ground.
2. A. The player is applying an unbalanced force to change the ball's state of motion.