Mechanics | Relativity Answers

Ok so I have a question which I don't quite understand. It's kinematics one.

A train is coming at the station. It starts deccelerating and passes first 50m in 5 seconds, and next 50 m in 7 s. Find acceleration and the starting velocity. I've studied it through, but cannot find the way to answer. I've got all formulas and equations.

a 200 kg load is hung on a wire of length of 4.00 m, cross sectional area 0.200 x 10^-4 m ^2 ,and Young's modulus 8.00 x 10^10 N/m^2.What is its increase in length?

a machine part at an angular of 0.060 rad/s its speed is then increased 2.2 rad/s at an angular acceleration of 0.70 rad/s.(a) Find the angle through which the part rotates before reaching this speed. (b) If both the initial and final angular speeds are double and the angular acceleration remains the same, by what factor is the angular displacement charged?why?

Spherical ball and solid cylinder have same mass and density. the moment of inertia will be greater for spherical ball or solid cylinder? Please answer me and explain the answer simply.

a race car acceleration from 0 m/s to 30 m/s with a displacement of 45 m. what is the vehicle's acceleration ?

what is the displacment of object performing simple harmonic motion when kinetic and potiential energy are equal?

Find an expression for the energy density in terms of stress and strain.

if a body is moving in a circular path with constant speed, what will be its acceleration constant or variable? please explain your answer in simple words.

A 38.0 kg child is in a swing that is attached to ropes 1.50 long. The acceleration of gravity is 9.81 m/s^2 . Find the gravitational potential energy associated with the child relative to the child's lowest position under the following condition: when the rope makes a 34.0 degree angle with the vertical.

A 38.0 kg child is in a swing that is attached to ropes 1.50 m long. The acceleration of gravity is 9.81 m/s^2 . Find the gravitational potential energy associated with the child relative to the child's lowest position under the following conditions: A) when the ropes are horizontal. b) when the ropes make 34.0 degree angle with the vertical.