Question

1. apply what you know
2. if you slide a toy car across the floor, it eventually stops because of:

a) inertia b) gravity c) friction d) air

1. when balanced forces act on an object, the object will:

a) speed up b) slow down c) not change motion d) spin

1. when unbalanced forces act on an object, it will:

a) stay still b) change motion c) float d) disappear

1. think and explain
2. newtons first law means that _.
3. a real - life example of inertia is _.
4. when forces are balanced, _.
5. when forces are unbalanced, _.

Explanation:

4. Apply What You Know

1.

• Step1: Analyze each option
• Inertia is the tendency of an object to resist a change in its state of motion. It doesn't make the toy car stop.
• Gravity acts vertically downward. While it affects the normal force (and thus friction indirectly), it's not the direct cause of the car stopping in the horizontal direction of its motion.
• Friction is a force that opposes the relative motion between two surfaces in contact. When the toy car slides on the floor, the frictional force between the car's wheels (or bottom) and the floor acts in the opposite direction of the car's motion, gradually reducing its speed until it stops.
• Air resistance is usually much smaller than the frictional force between the car and the floor for a toy - car sliding on the floor and is not the main reason for it to stop.

2.

• Step1: Recall the concept of balanced forces

According to Newton's first law, when balanced forces act on an object (\(\sum F = 0\)), the object will either remain at rest (if it was initially at rest) or continue to move with a constant velocity (if it was initially in motion). In other words, it will not change its motion.

• If the forces were un - balanced in the direction of motion, the object would speed up (if the net force is in the direction of motion) or slow down (if the net force is opposite to the direction of motion).
• Spinning would require a torque (a rotational force), which is not related to the concept of balanced forces in the context of linear motion (as described by Newton's first law for translational motion).

3.

• Step1: Recall the concept of un - balanced forces

When un - balanced forces act on an object (\(\sum F
eq0\)), according to Newton's second law (\(F = ma\), where \(F\) is the net force, \(m\) is the mass of the object, and \(a\) is the acceleration), the object will accelerate. Acceleration means a change in velocity (either a change in speed, a change in direction, or both).

• Staying still (\(v = 0\) and \(a=0\)) requires \(\sum F = 0\).
• Floating would imply a very specific balance of forces (like buoyancy and gravity in a fluid for an object floating), which is not related to the general concept of un - balanced forces.
• Disappearing is a physical impossibility in the context of classical mechanics (the forces we are discussing here).

5. Think and Explain

1.

Newton's First Law (the law of inertia) states that an object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity (in a straight line) unless acted upon by an un - balanced force.

2.

A real - life example of inertia: When a car suddenly stops, the passengers tend to keep moving forward. The passengers' bodies have a tendency to maintain their state of motion (the motion they had before the car stopped) due to inertia.

3.

When forces are balanced (\(\sum F = 0\)), the object will either remain at rest (if it was initially at rest) or continue to move with a constant velocity (if it was initially in motion).

4.

When forces are un - balanced (\(\sum F
eq0\)), according to Newton's second law (\(F = ma\)), the object will accelerate. This means a change in its velocity (either a change in speed, a change in direction, or both).

Answer:

4. Apply What You Know

1. c) Friction
2. c) Not change motion
3. b) Change motion

5. Think and Explain

1. An object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity (in a straight line) unless acted upon by an un - balanced force.
2. When a car suddenly stops, the passengers tend to keep moving forward.
3. The object will either remain at rest (if it was initially at rest) or continue to move with a constant velocity (if it was initially in motion).
4. The object will accelerate (a change in its velocity).