Kinetics/Motion in 2D/Energy question

  • Thread starter Curious&TheNon
  • Start date
In summary: You can't get time from that.In summary, we are given the specifications of a 12V car battery and a certain electric car that needs to maintain a speed of 48.3 km/hr. With a power requirement of 10.7 kW, and 11 batteries with 90.5% efficiency, we can calculate the distance this car can travel between recharges. Using the efficiency formula, we find that the batteries will last for a certain amount of time, but we cannot determine the exact distance without knowing the mass of the car.
  • #1

Homework Statement


A 12V car battery is capable of storing 3.51 kWh of electric energy. For a certain electric car to maintain a speed of 48.3 km/hr, it must develop 10.7 kW of power. If this car is run by 11 batteries which are 90.5% efficient, how far can this car travel, at the desired speed, between recharges?
V= 48.3 m/s (yes constant motion)
P=10700W
efficiency= 90.5%
Each battery capacity= 3510W
Uses 11 batteries

Homework Equations


E= (Wo / Wi ) *100[/B]
E= .5 * m * v^2
W= P*t

The Attempt at a Solution


1. Since its going at a constant velocity, i can find the mass. Using the Energy kinetic formula.
2.Finding the mass i can plug it into the efficiency formula to get its work output.
3. its using 11 batteries that are 90.5% efficient. So on the denominator of the efficiency formula it would be 11* 3510W because each capacity is 3.51kWh.
5.the numerator would be the Energy kinetic formula * 100 and then the efficiency would be 90.5%
6. Getting the time i could multiply it with the velocity to get its distance?
 

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  • #2
Curious&TheNon said:
Since its going at a constant velocity, i can find the mass. Using the Energy kinetic formula.
Since it's at constant velocity, the KE is constant. The energy from the batteries is not being used to add to KE, so it won't tell you the mass. Neither KE nor the mass are of interest here.
You are told how much power it needs to supply to the wheels, and you know the efficiency, so how much power must be drawn from the batteries?
How long can the batteries supply that power for?
 
  • #3
haruspex said:
Since it's at constant velocity, the KE is constant. The energy from the batteries is not being used to add to KE, so it won't tell you the mass. Neither KE nor the mass are of interest here.
You are told how much power it needs to supply to the wheels, and you know the efficiency, so how much power must be drawn from the batteries?
How long can the batteries supply that power for?

Okay ignoring the kinetic formula, my bad wasnt thinking straight. Re doing the effieciency formula it would be 90.5%= (10700W*100%/ (11* (3.51kWh*3.6E6)t)
 
  • #4
Curious&TheNon said:
Okay ignoring the kinetic formula, my bad wasnt thinking straight. Re doing the effieciency formula it would be 90.5%= (10700W*100%/ (11* (3.51kWh*3.6E6)t)
Using this formula we're able to calculate how long the batteries will last at the power to run the car.?
 
  • #5
Curious&TheNon said:
Okay ignoring the kinetic formula, my bad wasnt thinking straight. Re doing the effieciency formula it would be 90.5%= (10700W*100%/ (11* (3.51kWh*3.6E6)t)
Close, but if you check the dimensions you'll find it doesn't make sense. You have power/(energy*time).
 

1. What is the difference between kinetics and motion in 2D?

Kinetics refers to the study of forces and their effects on the motion of objects, while motion in 2D specifically refers to the movement of objects in two-dimensional space, taking into account both the horizontal and vertical axes.

2. How do you calculate the velocity of an object in 2D?

The velocity of an object in 2D can be calculated by dividing the displacement in the horizontal and vertical directions by the time taken to cover that displacement in each direction. The resulting values can then be combined using the Pythagorean theorem to find the total velocity.

3. What is a vector quantity in terms of energy?

A vector quantity in terms of energy refers to the amount of energy an object possesses in a specific direction. This can be represented by a vector, which has both magnitude (the amount of energy) and direction.

4. How is kinetic energy related to motion in 2D?

Kinetic energy is the energy an object possesses due to its motion. In 2D motion, kinetic energy is related to the object's velocity and mass, with the formula KE = 1/2 * m * v^2. This means that the faster an object is moving and the more mass it has, the greater its kinetic energy will be.

5. How does energy conservation play a role in 2D motion?

Energy conservation is a fundamental principle in physics that states that energy cannot be created or destroyed, only transferred or converted from one form to another. In 2D motion, energy conservation is important in understanding how the kinetic and potential energy of an object changes as it moves and interacts with other objects or forces.

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