Lesson Plan - Space Ship Pilot

The purpose of the Space Ship Pilot applet is to help students visualize the relation between acceleration and velocity in 2 dimensions. The concept of operating a spacecraft in a "weightless" environment is used to represent a situation without external forces, particularly the dissipative forces of air resistance and friction that make Newton's first law counter-intuitive.

The applet addresses the following common misconceptions among students of Physics:

• Acceleration and velocity are always in the same direction.
• Velocity is a force.
• If velocity is zero, then acceleration must be zero too.

The applet is designed to work with content in the following areas:

• Displacement
• Velocity and acceleration
• Vectors
• Components of vectors, coordinates
• Motion in one dimension
• Motion in two dimensions

The applet meets the following National Standards:  Science Content Standards: 9-12

• CONTENT STANDARD A:
• Use technology and mathematics to improve investigations and communications.
• Formulate and revise scientific explanations and models using logic and evidence.
• Recognize and analyze alternative explanations and models.
• Communicate and defend a scientific argument.
• CONTENT STANDARD B:
• Motions and forces

Sample Answers to Exercise Questions:

0. Accelerate the ship in one direction. Now slow the ship down to a halt. What direction did you have to accelerate the object in order to slow the ship down? The pilot must accelerate in the direction opposite of motion in order to halt the ship.
1. Is it possible to bring the ship to a halt using any other direction of acceleration other than what you found in exercise 1? No, any other direction will have a component of the acceleration which acts perpendicular to the direction of motion, and cause the ship to move to the side.
2. Accelerate the ship in one direction. What happens when you change the acceleration by 90 degrees? (i.e. start off moving forward, then accelerate directly to the left of the screen) The ship veers to the side.
3. In question 3, when you change the acceleration so that the ships thrusters are moving it left, does the speed at which the ship approached the top or bottom of the screen change? The component of the velocity in the up-down direction does not change if acceleration is at right angles (i.e. in the side to side direction)
4. Get the ship moving, and turn the thrusters off. Does the ship slow to a stop? No, Newton's first law states that an object in motion will continue in motion unless external forces act upon it. Here we are removing the external force of the thruster, and the ship will continue at the velocity it had when the thruster was turned off.
5. Answer the following questions true or false:
1. Velocity and acceleration are always in the same direction. False. When you slow down, the acceleration and velocity are in opposite directions.
2. The velocity is proportional to the force that is applied to an object. False, the acceleration is proportional to the force, Newton's second law.
3. Accelerating an object produces a change in the velocity. True, acceleration is defined as the rate of change of velocity
4. Accelerating an object speeds the object up. False, acceleration can increase, decrease, or change the direction of the velocity of an object.
5. When the applied force on an object ceases, the motion of the object ceases. False, the object will continue at the velocity it had when the force was removed, absent any other external forces.
Satellites orbiting the Earth have no air resistance or friction to slow them down, but they do not travel in a straight line path, instead they circle around the Earth. How can you explain this in terms of Newton's first law? Objects in space do feel the effect of gravity, that is, there IS an external force, and Newton's first law doesn't apply. In this case, gravity acts as an external force which keeps the satellite continuously "falling" around the Earth. This is different form the idea of weightlessness. Astronauts in space do feel the effect of gravity, it is what keeps them in orbit around the Earth, but they feel the exact same effect as the spacecraft they travel in, and thus are "weightless" with respect to the craft. The craft and the astronaut are said to be in "free fall".