Question

introduction: speed is a measure of how fast an object is moving. it is defined as distance moved per unit of time. in this gizmo, the units of speed are meters per second, or m/s.
question: what factors affect the speed of the sled?

1. observe: with the sled at 50.0 m, click play. observe the red sled speed speedometer.

what happens to the sleds speed as it moves down the slope? _
acceleration is a change in speed or direction over time. in what two ways does the sled accelerate as it descends? _

1. click reset. this time, focus on the speed of the sled after it reaches the bottom of the hill. click play. what do you notice? _

does the sled accelerate after reaching the bottom? _ explain. _

Explanation:

• When the sled moves down the slope, gravity acts on it. As it moves down, the component of gravitational force along the slope causes an increase in its speed.
• Acceleration is a change in speed or direction. As the sled descends, its speed increases (due to gravity pulling it down the slope) and its direction (initially it may be at rest or moving slowly, and as it goes down, the direction of motion is more along the slope's incline).
• After reaching the bottom of the hill, on a flat surface (assuming no other forces like a motor), there is no net force in the direction of motion (gravity acts perpendicular to the direction of motion on a flat surface and if we assume no external driving force). According to Newton's first law, an object in motion will stay in motion with a constant velocity if there is no net force acting on it. So the speed of the sled remains relatively constant (assuming no significant friction changes etc., in a simple model).
• Since there is no change in speed (assuming ideal conditions with no net force in the direction of motion) and no change in direction (it's moving in a straight line on the flat), there is no acceleration. Acceleration is \(a=\frac{\Delta v}{\Delta t}\), and if \(\Delta v = 0\) (no change in velocity), then \(a = 0\).

Answer:

• What happens to the sled's speed as it moves down the slope? The sled's speed increases.
• In what two ways does the sled accelerate as it descends? The speed of the sled increases and its direction of motion changes (more along the slope as it moves down).
• What do you notice after reaching the bottom of the hill? The speed of the sled remains relatively constant (assuming no external forces like a motor or significant non - gravitational forces in the direction of motion).
• Does the sled accelerate after reaching the bottom? No. Explain: There is no net force in the direction of motion (assuming ideal conditions with no external driving force and gravity acting perpendicular to the direction of motion on a flat surface), so \(\Delta v=0\) (no change in velocity) and \(a = 0\) (since \(a=\frac{\Delta v}{\Delta t}\)).