Kinematics problem: Determine the velocity of this car during braking

In summary, the conversation discussed the process of integrating a function and finding the integration constant. It was mentioned that the velocity of a car at t=0s was 30m/s and this information was used to determine the value of the integration constant. The conversation also calculated the velocity at t=4s and found it to be -101.2m/s, but upon further examination, it was realized that there was a mistake in the first step and the correct value should be -0.2t3. After correcting this error, the velocity at t=4s was recalculated to be 1.2m/s.
  • #1
dbag123
76
3
Homework Statement
Car starts to brake at t=0s from 30m/s Determine the velocity of the car at 4s and the integration constant
Relevant Equations
a(t)=-0.6t^2+2t-8 (m/s^2)
Step 1. Integrate the function --> it comes out to -1.8t3+t2-8t+c
Step 2. Figure out the integration constant --> I know that the velocity of the car is 30m/s at t=0s so making 30m/s = -1.8(0s)3+(0s)2-8(0s)+C it would seem that C is 30m/s
Step 3. Calculate velocity at 4s --> V(4s)= -1.8(4s)3+(4s)2-8(4s)+30m/s and that equals to -101.2m/s
Am i in the right?
 
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  • #2
You should have a second look at your first step. What do you get if you take the derivative of your result?
 
  • #3
allrighty it is wrong it should be -0.2t3...
integration constant does not change but the v(4s) now becomes 1.2m/s
it should be right
 

1. What is Kinematics?

Kinematics is the branch of physics that studies the motion of objects without considering the forces that cause the motion. It deals with concepts such as displacement, velocity, acceleration, and time.

2. What is the velocity of an object in motion?

Velocity is a measure of how fast an object is moving and in what direction. It is calculated by dividing the displacement of the object by the time taken to cover that distance. In other words, it is the rate of change of an object's position with respect to time.

3. How is velocity determined during braking?

During braking, the velocity of a car is determined by dividing the change in its speed by the time it takes to come to a stop. This can be calculated using the equation v = (vf - vi)/t, where vf is the final velocity, vi is the initial velocity, and t is the time taken.

4. What factors can affect the velocity of a car during braking?

The velocity of a car during braking can be affected by various factors such as the initial speed of the car, the friction between the tires and the road, the condition of the brakes, and any external forces acting on the car.

5. How can the velocity of a car be changed during braking?

The velocity of a car can be changed during braking by altering the force applied to the brakes or by changing the surface the car is driving on. This can result in a change in the friction and ultimately affect the deceleration and velocity of the car.

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