**Air/water Rocket**

The choice of propellant for this toy rocket makes a huge difference in thrust.

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Read more about Air/water Rocket1 Oxford St Cambridge MA 02138 Science Center B-08A (617) 495-5824

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The choice of propellant for this toy rocket makes a huge difference in thrust.

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Read more about Air/water RocketA motorized fan mounted on a reaction cart blows air into a "sail" which is also mounted on the cart. Which way will the cart move?

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Read more about Sailboat Reaction CartRadio controlled car moves one way while road moves the other.

We tell our students that, when a car drives down the road, the road and the Earth move in the opposite direction, albeit imperceptibly. This demonstration is a realization of that concept, made possible (and perceptible) by the fact that the road is *not* attached to the Earth.

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Read more about Reactionary RoadbedA straightforward demonstration of Newton's 3rd law, that forces are interactions and thus come in pairs.

Two people, each sitting (cross-legged) on their own board, position themselves in the center of the track facing each other. Upon pushing against each other with their hands, they glide apart down the length of the track. Repeat this with one person turned around — the other person pushes on his/her back instead of pushing against each other with their hands. The ensuing motion down the track is exactly the same as before.

... Read more about Reaction on Conveyor TrackCalculation of gravitational constant, with accompanying apparatus model.

The gravitational attraction between lead spheres. The data from the demonstration can also be used to calculate the universal gravitational constant G.

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Orbital motion simulated by ball rolling on wooden potential well.

Motion in a central potential is demonstrated by a ball rolling on a circular 1/r curved surface.

The 1/r potential well simulates the gravitational potential surrounding a point mass; a ball bearing moving in this potential follows a parabolic or elliptical orbit depending upon its initial trajectory and velocity. As it loses energy due to friction, the orbit decays and the ball spirals towards the centre of the well. You could...

Read more about Potential WellA physical pendulum with two adjustable knife edges for an accurate determination of "g".

An important application of the pendulum is the determination of the value of the acceleration due to gravity. By adding a second knife-edge pivot and two adjustable masses to the physical pendulum described in the Physical Pendulum demo, the value of g can be determined to 0.2% precision.

Using a simple pendulum, the value of g can be determined by...

Read more about Reversible (Kater's) PendulumFalling in an evacuated tube at the same rate.

In the absence of air resistance all bodies, regardless of size or weight, fall with the same acceleration at the same point above the Earth. Here a feather and a dime (see *Comments*) fall under the influence of gravity in an environment where there is no air to mess things up.

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Read more about Feather and DimeAllow a board to rotate under the force of gravity and the free end will accelerate at a rate greater than *g*. Relation between angular acceleration and linear acceleration seems to give free-fall paradox.

If a board, held in a vertical position with one end resting on the...

Read more about Falling Faster than 'g'The tension force in a rope grows exponentially with the number of turns the rope makes around a pole.

Apple electronically released from platform; fall time given by special circuit and digital display.

This is a free-fall-from-rest experiment in which an apple (or any other object of comparable size) is dropped from the lecture hall ceiling into a catching bucket on the floor. By measuring the (1) distance and (2) duration of the fall, an accurate (± 0.022%) determination of the acceleration due to gravity can be made:

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Straight and cycloidal inclined paths, with the ball on the cycloidal path always beating the straight one to the bottom.

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Prediction of motion of masses in a more complex pulley/mass assembly.

**What it shows:** This compund Atwood's Machine demonstrates an old and interesting problem. The two small weights on the right side are not of equal mass — one is 100 g and the other...

Combinations of weights suspended over pulley to show that asymmetry causes acceleration.

Image on the left, of a lightweight plastic pulley with balanced 50 g brass weights, and on the right, the pulley in motion as the unbalanced weights accelerate.

Ball rolling down tilted trough in oscillatory fashion yields acceleration. Also known as Galileo's Inclined Plane).

- Electrostatics (7)
- Electric Fields and Potential (8)
- Electric Currents; DC Circuits (9)
- Fields of Moving Charges (4)
- Magnetic Fields and Forces (2)
- Induction and Faraday's Law (13)
- Electric Fields in Matter (2)
- Magnetic Fields in Matter (7)
- Electromagnetic Waves (7)
- Electromagnetic Devices (1)
- AC Circuits (6)

- Measurement and Kinematics (10)
- Center-of-Mass and Relative Motion (4)
- Forces in Equilibrium (15)
- Simple Machines (4)
- Newton's First Law (4)
- Newton's Second Law, Gravity and Friction Forces (19)
- Newton's Third Law (5)
- Impulse, Work, and Energy (4)
- Conservation of Linear Momentum and Energy (12)
- Angular Momentum (9)
- Rotational Dynamics (moment of inertia and the action of torques) (9)
- Rotational Dynamics (centripetal forces and rotating reference frames) (9)
- Strength of Materials and Properties of Matter (5)

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