Calculating Thrust and Resistance

In summary, the conversation discussed building a boat for a physics class project and conducting two experiments to calculate the thrust of the motor and the resistance of the hull. The first experiment involved dropping a 20g mass to determine the resistance, and the second experiment involved tying the string to the back of the boat with a 20g mass to measure thrust. The boat has a mass of 0.154Kg. The equation F=ma was used to calculate the forces of gravity and acceleration in both experiments. The next steps would be to draw a picture of the experiments and determine the resulting forces on the boat and stone to find the resistive force and the difference between thrust and resistive force.
  • #1
sammycs
1
0

Homework Statement


i built a boat for physics class with an electric motor. we are asked to calculate the thrust of the motor and the resistance of the hull using Newton's second law of motion. i conducted an experiment (to collect data in order to find resistance) that required a string attached to the front of the boat in a trough of water (which was placed up off the ground) with the motor turned off. the string had a 20g mass on the end of it. when we let the mass fall to the ground, it took 2.35s to fall .88m. i conducted another experiment (to collect data in order to measure thrust) and tied the string to the back end of the boat with the motor turned on. there was a 20g mass tied on the end of the string again. we measured a .1m length in the trough and found out that the boat moved .1m backwards in 1.33s. Key information: the boat has a mass of .154Kg

Homework Equations


d= Vi X t + 1/2 A t(squared)
Fg= mg
F=ma
F = Fapplied + Ffriction?
probably others but I am unsure

The Attempt at a Solution


FIRST EXPERIMENT TO FIND RESISTANCE
calculated the force of gravity acting upon the mass ---> .196N
calculated the acceleration of the mass falling .88m in 2.35s ---> .32m/s(squared)

SECOND EXPERIMENT TO FIND THRUST
calculated the force of gravity acting upon the mass ---> .196N
calculated the acceleration of the mass falling .1m in 1.33s --->.113m/s(squared)

WHAT SHOULD MY NEXT STEPS BE? thanks so much
 
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  • #2
Draw a picture of both experiments and show what forces act on the boat and stone. These forces determine the acceleration of the whole system and you can find the resistive force in the first case and the difference between thrust and resistive force in the second case.

ehild
 

FAQ: Calculating Thrust and Resistance

How do you calculate thrust and resistance in a fluid?

To calculate thrust and resistance in a fluid, you will need to use the equations for Newton's second law of motion and Bernoulli's principle. First, determine the mass of the fluid being moved and the velocity of the fluid. Then, use Newton's second law to calculate the force of thrust. For resistance, use Bernoulli's principle to calculate the pressure difference between the front and back of the object, and then use the equation for drag force to determine the total resistance.

What factors affect the calculation of thrust and resistance?

The main factors that affect the calculation of thrust and resistance are the mass and velocity of the fluid, the shape and size of the object, and the properties of the fluid such as density and viscosity. Other factors that may also play a role include the angle of attack, surface roughness, and turbulence in the fluid.

How does thrust and resistance impact the movement of an object in a fluid?

Thrust and resistance play opposing roles in the movement of an object in a fluid. Thrust is the force that propels the object forward, while resistance is the force that opposes the movement of the object. The balance between these two forces determines the overall motion of the object, with greater thrust resulting in faster movement and greater resistance resulting in slower movement.

Can you calculate thrust and resistance for different types of fluids?

Yes, the equations for calculating thrust and resistance can be applied to different types of fluids, including liquids and gases. However, the properties of the fluid, such as density and viscosity, will affect the magnitude of these forces. For example, a more viscous fluid will result in greater resistance, while a less dense fluid will require less thrust to achieve the same velocity.

How can you use the calculations of thrust and resistance in practical applications?

The calculations of thrust and resistance have many practical applications, particularly in the fields of aerospace engineering and marine technology. These calculations can be used to design more efficient and effective vehicles, such as airplanes, ships, and submarines. They can also be used to optimize the performance of engines and other propulsion systems by determining the necessary thrust to overcome resistance and achieve the desired speed or movement.

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