HELP w/ Kinematics Problems?

  • Thread starter dagitt
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In summary, the given problems involve finding the time, speed, initial velocity, and distance using the standard constant acceleration equations.
  • #1
dagitt
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HELP w/ Kinematics Problems??

Homework Statement


a) A baseball is thrown horizontally at 45m/s. The ball slows down at a rate of 5m/s^2. How long is the ball in the air before coming to rest?

b) A pile driver drops from a height of 35m before landing on a piling. What is the speed of the driver when it hit the piling?

c)A meteor falls from the sky to Earth. The meteor already had an initial velocity downward when it was spotted. If it hit the Earth at 335m/s after being seen for 30 seconds, then what was the initial velocity of the meteor?

d) A car started from a rest and accelerated at 9.54m/s^2 for 6.5 seconds. How much distance was covered by the car?


Homework Equations


a) a = change in velocity/time
b) speed = d/t
c) final velocity = initial velocity + (acceleration*time)
d) a & s


The Attempt at a Solution


a) a = 5m/s^2, v = 45m/s...now what??
b) speed = 35/t...NOW WHAT?
c) 335 = vi + (a*30)...now what?? is this even right?
d) (6.5)2 is 42.5s2...so is 42.5m the answer??


Physics completely baffles me. I'm not a math person at all. Any or all help would be GREATLY appreciated, thanks so much...
 
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  • #2
Welcome to PF!

Hi dagitt! Welcome to PF! :wink:

For each question, use the standard constant acceleration equations (using g as the acceleration for questions b) and c) ) :smile:
 
  • #3


Hello,

I would be happy to help you with your kinematics problems. In order to solve these problems, we need to use the kinematic equations, which relate the variables of displacement, velocity, acceleration, and time.

a) For this problem, we have the initial velocity (v0) of 45m/s and the acceleration (a) of -5m/s^2 (since the ball is slowing down). We also know that the final velocity (vf) is 0m/s, since the ball comes to rest. We can use the equation vf = v0 + at to solve for the time (t) it takes for the ball to come to rest. Rearranging the equation, we get t = (vf - v0)/a. Plugging in the values, we get t = (0 - 45)/(-5) = 9 seconds. So the ball is in the air for 9 seconds before coming to rest.

b) For this problem, we can use the equation vf^2 = v0^2 + 2ad to solve for the final velocity (vf) when the pile driver hits the piling. We know that the initial velocity (v0) is 0m/s since the pile driver is dropped from rest. We also know the displacement (d) is 35m and the acceleration (a) is due to gravity, which is -9.8m/s^2. Plugging in the values, we get vf^2 = 0 + 2(-9.8)(35) = -686. Taking the square root of both sides, we get vf = 26.2m/s. So the speed of the pile driver when it hits the piling is 26.2m/s.

c) For this problem, we can use the equation d = v0t + 1/2at^2 to solve for the initial velocity (v0) of the meteor. We know that the final velocity (vf) is 335m/s, the time (t) is 30 seconds, and the acceleration (a) is due to gravity, which is -9.8m/s^2. Plugging in the values, we get 335 = v0(30) + 1/2(-9.8)(30)^2. Solving for v0, we get v0 = 335 - 1/2(-
 

What is kinematics?

Kinematics is the branch of physics that deals with the motion of objects without considering the forces that cause the motion.

What types of problems can be solved using kinematics?

Kinematics can be used to solve problems involving displacement, velocity, acceleration, and time for objects moving in a straight line or along a curved path.

What are the basic equations used in kinematics?

The basic equations used in kinematics are: d = v0t + ½at2, v = v0 + at, and v2 = v02 + 2ad, where d is displacement, v is velocity, a is acceleration, t is time, and v0 is initial velocity.

How do I know which equation to use for a specific kinematics problem?

In order to determine which equation to use, you need to identify the known and unknown variables in the problem. Then, choose the equation that includes those variables and solve for the unknown variable.

What are some common mistakes to avoid when solving kinematics problems?

Some common mistakes to avoid when solving kinematics problems include using incorrect units, not considering the direction of motion, and using the wrong equation for the given problem. It is important to carefully read and understand the problem before attempting to solve it and to double-check your calculations for accuracy.

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