Kinematic Definition and 406 Threads

When doing SUVAT problems, why does the item which begins motion later given a time "t-x" where x>0. For example, if dropping a ball, and then dropping another ball 5 seconds later, the first ball's time can be expressed as "t" and the second ball's time as "t-5". Why is it not t+5? Thanks

M. Chodorowski argues in his http://arxiv.org/abs/astro-ph/0610590v3" that the concept of "expansion of space" is not necessary to explain the expansion of the universe, and therefore Occam's Razor tells us that we should consider discarding the concept entirely. He says that expansion is...

hard kinematic problem, need...help...pls:) Homework Statement A policeman (on a motorcycle, with the engine going) is hiding behind a bush on the side of the road when a speeding truck passes with a speed of 96.5 km/h. As the truck passess he sets off with an acceleration of 1.83 m/s, which...

kinematic question, i think it's hard:( Homework Statement Two camels leave the spinx at time 52.5 s apart. The first moves off with a uniform acceleration of 1.30 m/s2, which it maintains for 1.92 s. It then continues with the acquired speed. The second camel moves of with a uniform...

Homework Statement A bell is thrown vertically upwards with speed 10m/s from a point 2 m above horizontal ground. a) calculate the length of time for which the ball is 3m or more above the ground Homework Equations kinematic ones The Attempt at a Solution We I wanted to find the...

Homework Statement If we have a velocity-time graph that is negatively accelerating, how would we draw the graph for the acceleration time graph? Would we draw it below zero because it is negatively accelerating (negative number). The picture of the graph is attached. The Attempt...

[SOLVED] Kinematic motion problem Homework Statement A police car stopped at a set of lights has a speeder pass it at 100 km/h. If the police car can accelerate at 3.6 m/s^2, a) how long does it take to catch the speeder? b) how far would the police car have to go before it catches the...

[SOLVED] Kinematic motion problem. (acceleration, displacement, velocity) Homework Statement Two rugby players are running towards each other. They are 37 m apart. If one is accelerating from rest at 0.5 m/s^2 and the other was already moving at 3.1 m/s and maintains her speed. (brackets are...

[SOLVED] Kinematic Equations This is the question. I have sat here and tried to figure out how to even start this problem for hours. I can't seem to get it through my head. If someone could help me set it up, I can figure out the rest I think. Thanks in Advance. Q. A car and a...

[SOLVED] Different values with rotational kinematic equations Hello everyone, I got two different values for final angular speed when I tried to use the third and fourth kinematic equations. I filled the template here with the problem with my attempts. Homework Statement A bicycle wheel of...

Hey, Would anyone be able to solve this Kinematic Problem? At least approximately. The mechanism in question is a cylinder, piston and a slider. The cylinder is fixed on a pivot in the middle of its body, obviously from the outside. I have found some approximate solution, but I am...

okay, this is simple and i feel ridiculous for asking, but I'm reviewing for my final and i do not remember how to do this type of problem.. Runner A runs toward a flag pole at a constant speed of 5.0 m/s. Runner B begins to run toward the flagpole at 3.0 m/s^2 when Runner A is 15 m ahead...

Homework Statement For this project, we had to build a vehicle that would hold an egg, and drop it a distance of about 40 feet, and making sure the egg wouldn't break. There are various parts to the report part of this project, and I had a question about the first part. Basically, one part...

A ball of mass 0.5 kg, initially at rest, is kicked directly towards a fence from a point 32 meters away. The velocity of the ball as it leaves the kicker's foot is 20 meters per second at an angle of 37 degrees above the horizontal. The top of the fence is 2.5 meteres high. The kicker's foot is...

Homework Statement A canonball is launched up in the air with velocity v_0. There is air resistance, which is equal to kmv (where k is some proportionality constant and m is the mass of the canonball) and is proportional to the canonball's velocity. How long does it take to reach its maximum...

Homework Statement An object is thrown up from the top of a building 50 m high. It rises to a maximum high of 20 m above the roof. A) when does it land on the ground B) At what velocity does it land ? C) When is it 20 m below the roof? Homework Equations The 4 kinematics equations...

Homework Statement A 1.0kg wood block is launched up a wooden ramp that is inclined at a 38 degree angle. The block's initial speed is 14 m/s. (Use uk = .20 for the coefficient of kinetic friction for wood on wood.) a.) What vertical height does the block reach above its starting point...

hello, i'm having trouble with kinematic equations. i feel that i understand them, but when i get to a problem, I'm so confused. i can figure out what i have and what i don't have, but it's choosing the correct formula that is my main problem. how do i know when to solve for what...

Can they be used if the acceleration is = to zero?? I know that they can only be used if the acceleration is constant but is zero considered a constant?? Thanks =):confused:

Kinematic problem help! Homework Statement David is driving a steady 31.0 m/s when he passes Tina, who is sitting in her car at rest. Tina begins to accelerate at a steady 2.80 m/s^2 at the instant when David passes. How far does Tina drive before passing David? What is her speed as...

Homework Statement A Rocket initially at rest on the ground accelerates straight upward from rest with constant net acceleration a, until time t_1 where fuel is exhausted. Homework Equations The Attempt at a Solution I thought that putting these values into the kinematic...

Homework Statement The height of a helicopter above the ground is given by h = 2.60t3 , where h is in meters and t is in seconds. After 2.00 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground? Homework Equations yf=y(initial) +...

Homework Statement Derive (v_f)^2 = (v_i)^2 +2ad Homework Equations (v_f)^2 = (v_i)^2 + 2ad (v_f) = (v_i) + at d = (v_i)t + \frac{1}{2}at^2 The Attempt at a Solution I have attempted to replace the variables with others from other kinematic equations such as v_f = v_i + at...

Homework Statement A group of people are watching a fireworks display. 3.5 s after they hear a rocket launch, they see the explosion. the explosion is observed to be located 50.0 from the launch point at an angle of 73.0 degrees above the horizontal. (a) Sketch the problem. Label all...

Homework Statement A ball is thrown vertically upwards with a speed of 10m/s from a point of 2m above the horiztonal ground. a) Calculate the length of time for which the ball is 3m or more above the ground. Homework Equations v^2=u^2 + 2as v=u+at The Attempt at a Solution So there's...

Homework Statement if you knew that the acceleration of a body is inversely proportional with square the time from the time interval (t=2'' to t=10''), and at t=2'' its velocity was V=-15 m/sec., and at t=10'' its velocity was V=-0.36 m/sec. if its postion from the origin point at t=2'' is...

Hi everyone, i have a exam coming up for Physics and this question from the kinematic unit is really bothering me. I've tried many times but i have no idea how to solve it. Some help would be greatly appreciated, thanks. :smile: Homework Statement Question: Town A and Town B are 6.0 x 10^2...

Homework Statement After falling from rest a a height of 30 m, a 0.50 kg ball rebounds upward, reaching a height of 20 m. If the contact between ball and ground lasted 2.0 ms, what average force was exerted on the ball? Homework Equations The Attempt at a Solution I figured I had to...

A wheel 60.0 cm in diameter accelerates uniformly from 245 rpm to 395 rpm in 7.5 s. How far will a point on the edge of the wheel have traveled in this time? I keep getting 125.66, I don't really understand what forumal to use.

Hello, the question I'm having trouble with is: "A 8.00kg block of ice, released from rest at the top of a 1.5 m long frictionless ramp, slides downhill, reaching a speed of 2.5 m/s at the bottom. What is the angle between the ramp and the horizontal?" My first attempt to solve this...

Can you please help me out with this problem?!? Suppose that a 1000 kg car is traveling at 25 m/s (about 55 mph). It brakes can apply a force of 5000 N. What is the minimum distance required for the car to stop. :confused:

Work?...maybe just kinematic...(please help! I don't even know what it is!) The spring shown in the figure is compressed 50 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30 degree...

Hi, I'm new to this forum. I need major help on my homework. So the kinematic equation, Vf² = Vi² + 2ad I need to figure out how to manipulate it so I can find Vf(final velocity), Vi(initial velocity), a(acceleration), and d(displacement). I figured to find Vf, you just square root it...

Im a 1st year physics student in the 11th grade. I haven't had much trouble with the assignment, but for some reason i cannot get the correct solution on this problem. A certain car is capable of accelerating at a rate of 0.57 m/s2. How long does it take for this car to go from a speed of 53...

I am so confused right now. This is porbably a really easy question to answer but I'm just too stupid to understand it... So onto my question..a car drives 120km/h from point A to B (which is 150km). When does a second car need to leave from point C (which is in between point A and B and...

This is a problem that appeared quite simple but is for some reason incorrect. I am not quite sure where I made my mistake so I spelled out my thought process below: Question: "Suppose that a cart was released from rest at a position of 3.5 cm down the ramp and continued to travel down the...

I'm a little confuse about these. velocity as a function of time, displacement as a function of time and velocity as a function of displacement. I know how to use this formulas, but in my lab there is a question that I am stuck on. How are this kinematic equations related to each other? and...

I am currently studying Kinematic Chapter and I am facing problem in the following question: The initial velocity of a particle is 15ms-1 along the Ox direction(Ox is a straight line). After 5.0 s its velocity is 15 ms-1 at an angle of 60 degree to the Ox direction. Find the magnitude and...

Question 3 A toy rocket is fired vertically upwards with an initial velocity of 29.2 ms-1. Calculate how long (in s) the rocket stays in the air before it returns to the ground. s=? u=29.2 v=0 a=-g t=? i've used t=(v-u)/a and then multiplied the answer by 2 is this the correct method...

The human body can survive a negative acceleration trauma incident if the magnitude of the acceleration is less than 250 m/s^2. If you are in an automobile accident at an initial speed of 96 km/h and are stopped by an airbag that inflates from the dashboard, over what distance must the airbag...

I just can't seem to figure this one out. From the top of a tall building, a gun is fired. The bullet leaves the gun at a speed of 340m/s, parallel to the ground. The bullet puts a hole in a window of another building at "x" distance away, and hits a wall that faces the window that is "6.9m"...

An olympic long jumper leaves the ground at an angle of 23 and traveled a distance of 8.7m before landing. Find the speed at takeoff. Ok, so I've tried to plug in datas in formulas but i keep getting the wrong answer. The answer is suppose to be 11 m/s. CAn someone guide me in a step by step...

In this problem, it states that Michael Jordan is able to jump and remain in the air for two full seconds from launch to landing. Use that information to calculate the maximun height that such jump would attain. It also says that MJ's jaximum jump height has been estimated at about one meter...

Q: an object is thrown from the ground into the air with a velocity of 20.0m/s at an angle of 27.0 degrees to the horizontal. what is the max height reached by this object? i drew the triangle and found vertical side to be 9.08 m/s and horizontal side to be 17.8m/s using sin and cos...

Physics Kinematic Problem -- need help Well here I am studying for the final and this question pops up and I have no idea how to do it. I know the answer however, but it does not really help me. If you walk 6.0 km in a straight line in a direction north of east and you end up 2.0 km east and...

Hello, Sorry about this and please don't think I m a lazy guy who is posting an assinment that is due tomorrow. I m scanning it and posting this because these questions do not involve numbers but require reasoning in which i m bad at. I m currenly taking a Physics 2nd year distance ed course...

I'm working on this problem and I've came up with a solution but however I couldn't find anything else to verify the problem so if you could let me know if I did it correctly and help me on the right track what would be super. The problem goes as folllow: A player is shooting a ball into a...

Hi,really need help with this question. A motorist traveling at 13 m/s aprroaches traffic lights which turn red when he is 25m away from the stop line.His reaction time(i.e. the interval between seeing the red light and applying the brakes)is 0.7s and the condition of the road and his tyres is...

Hi all, can some one please help me on this problem; The acceleration of a marble in a certain fluid is proportional to the speed of the marbles, and is given (in SI units) by a= -3.00V^2 for v>0. If it enters this fluid with a speed of 1.50 m/s, how long will it take for the marble to reach...

in a kinematic equation when you throw a ball up and it reaches its highest point its velocity becomes zero how long is it zero