# Solve Kinematic Problems: Tips & Advice

• HWGXX7
In summary, the conversation is about a self-study on mechanics and the problem of finding the time it takes for an object to go from an initial velocity/position to a final velocity/position, as well as the time it takes for the object to decelerate to zero velocity at a certain position. The equations for velocity and position are mentioned and the solution to the problem is calculated. The final travel time is determined to be 44.73 seconds. The person thanks for the help and mentions that the problem was relatively easy.
HWGXX7
Hello,

I'am doing some selfstudy to aqcuire more experience with mechanics. I got a geat book I'am currently reading. But got stuck in a question I can't answer...

I hope you guys can get me on the good track, just need an approach to tackle te problem. Did already solve problems,but this one seems odd to me...So I wait for good tips. Thank you.

you have an initial velocity/position 200*10^3, 600
you know that deceleration is constant
you have a final velocity/position 50e3, 586

find the time it takes to go 14 feet with constant deceleration from 200e3 to 50e3

then, at 30 meters, he decelerates again, to zero m/s
so find that time, and sum them up

$$a=constant, v(t)=-a.t+v_{0}, x(t)=-a\frac{t^{2}}{2}+v_{0}.t+x_{0}$$
Initial conditions:
$$v_{0}=55.56 m/s$$
$$x_{0}=0 m$$
Situation after $$t_{1} sec.$$:
$$v(t_{1})=13.89 m/s$$
$$x_(t_{1})=14 m$$

Rewrite equations:
$$-a.t_{1}=13.89-55.56=-41.67 m/s$$
$$14=(-41.67).\frac{t_{1}}{2}+55.56.t_{1}=(-20.84+55.56).t_{1}$$

Solution:
$$t_{1}=0.4032 sec.$$
This answer is the input to the velocity equation to get the constant decceleration, which is $$103.3m/s^{2}$$

Travel time to reach the 30m position: $$\frac{556m}{13.89 m/s} = 40.03 s$$

Total travel time so far: $$40.43 s$$
The decceleration time tot reach ground level can be get with the same procedure.
Total travel time: $$44.73 s$$

Thank for the good help, relative easy problem actually.

## 1. What are kinematic problems?

Kinematic problems involve using equations and principles of motion to solve for unknown variables such as distance, velocity, and acceleration.

## 2. What are some tips for solving kinematic problems?

Some tips for solving kinematic problems include drawing a diagram, labeling known and unknown variables, using the correct equations, and checking units for consistency.

## 3. How do I know which equation to use for a kinematic problem?

The equation to use for a kinematic problem depends on the known variables and what you are solving for. It is important to identify the variables and choose the appropriate equation that relates them.

## 4. What are some common mistakes to avoid when solving kinematic problems?

Some common mistakes to avoid when solving kinematic problems include mixing up units, using the wrong equation, and making calculation errors. It is also important to pay attention to the sign convention for direction.

## 5. Can you provide examples of kinematic problems and their solutions?

Yes, here is an example problem: A car is traveling at 25 m/s and decelerates at a rate of 5 m/s^2. How long will it take for the car to come to a complete stop? Solution: Using the equation vf = vi + at, we can solve for time: 0 = 25 + (-5)t. Solving for t, we get t = 5 seconds.

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