Mechanics | Relativity Answers

A train travelling along a straight track starts from rest at point A and accelerates uniformly to 20m/s in 20s. It travels at this speed for 60s then slows down uniformly to rest in 40s at point C. it stays at rest at C for 30s, then reverses direction accelerating uniformly to 10m/s in 10s. It travels at this speed for 30s, then slows down uniformly to rest in 10s when it reaches point B.
a) Plot a graph of the motion of the train
b) Use your graph to calculate
i) The trains displacement from point A when it reaches point C
ii) The trains displacement from point A when it reaches point B
iii) The trains acceleration each time its speed changes

An aircraft heads north at 320km/h relative to the wind.the wind velocity is 80km/h from the north.find the velocity of the aircraft relative to the ground.

On a beautiful summer night a pensive and motionless raccon is watching a log floating down an indolent river with a velocity of 1.5 m/s, East 25 degrees North relative to the racoon. The racoon also notices that a pesky muskrats is approaching the log at a velocity of 3.75 m/s, South 40 degrees East relative to the racoon in an attempt to scare an innocent frog sleeping on the log. If the frog wakes up in time and tries to evade the muskrats by “running” along the log with a velocity of 0.3 m/s straight South relative to the log, find the frog’s velocity with respect to the racoon.

You're on a rooftop and you throw a ball downward below and another upward. The second ball, after rising, falls and strikes the ground below. If air resistance can be ignored, and if your downward and upward speeds are the same, how do you think the speeds of the balls compare upon striking the ground. use energy considerations when answering.

A particle is moving in the xy-plane with velocity v(t)= vx(t)i + vy(t)j and acceleration a(t)=ax(t)i + ay(t)j. By taking the appropriate derivative show that the maginitude of v can only be constant if axvx + ayvy = 0

You run 100 m in 12 s, then turn around and jog 50 m back toward the starting point in 30 s.
a. Calculate your average speed.

A car starts from a check point P and comes to rest at a check point Q,8km away in 4 minutes. It has first, a uniform acceleration for 50 seconds, then a constant speed, and brought to rest with uniform retardation after 30 seconds. Sketch a velocity time graph for the motion and find,maximum speed, acceleration and retardation.

An object at rest is acted by a 8.0N force for 0.40s after this time interval, the object has a final speed of 8.0m/s. How much time is needed for 4.0N force to produce the same speed?

A 5kg object which is initially at rest is acted upon by a 25N net external force. What is the speed of the object after 4 seconds?

An airplane starts from rest and accelerates on a runway at 5m/s^2 for 7 seconds. How far down the runway is the plane after 7 seconds?