Mechanics | Relativity Answers

A motorist is travelling at 15 m/s when he sees a child run into the road. He brakes and
the car comes to rest in 0.75 s.
a) Draw a velocity time graph to show the deceleration, and use your graph to
calculate the distance travelled once the brakes are applied [4]
b) The deceleration of the car.

An object of mass 10kg on a flat horizontal surface is pulled with a force of 70N at an angle of 30 degrees above the horizontal. The object slides along the surface with an acceleration coefficient of k.e is 0.3. What is the normal force.

A ship steams due west at the rate of 15 kmph when the river is flowing at the rate 6 kmph due south. What is the velocity relative to the ship of a train going due north at the rate of 30 kmph?

A hydroelectric power plant uses spinning turbines to transform the kinetic energy of moving water into
electric energy with 80 % efficiency. That is, 80 % of the kinetic energy becomes electric energy. A small
hydroelectric plant at the base of a dam generates 50 MW of electric power when the falling water has a
speed of 18 m/s.
What is the water flow rate -kilograms of water per second-through turbines?

. a. Starting from rest, a crate of mass m is pushed up a frictionless slope of angle u by a horizontal force of
magnitude F. Use work and energy to find an expression for the crate’s speed v when it is at height h
above the bottom of the slope.
b. Doug uses a 25 N horizontal force to push a 5.0 kg crate up a 2.0 m high, 20o
frictionless slope. What
is the speed of the crate at the top of the slope?

a. How much work must you do to push a 10 kg block of steel across a steel table at a steady speed of 1.0
m/s for 3.0 s?
b. What is your power output while doing so?

Kinematics equations:

1. An angry scaffolder throws her spanner down to the ground with a velocity of 2 ms-1
the spanner takes 2 seconds to strike the ground.
Calculate the height the scaffolder was at when she threw down the spanner.

2. An experimental rocket is launched vertically with a velocity of 5ms-1
At a certain height the tail falls off and strikes the ground after 4 seconds.
Assuming the tail falls off while the rocket is travelling at 5 ms-1, calculate the height at which it
fell off.

what are the postulates of special theory of relativity? drive Lorentz transformation equation with their help.
Expert's answer

Thank you for your help and thank you for your patience. It means a lot to me.
I’m still having a hard time reconciling.

Would it be accurate to say that if object A and object B were “floating” inertially in deep space, and a force accelerated object B away from object A at some velocity, that the clock in object B would tick slower than the clock in object A?

A "ship A" steaming in a direction 030° with a steady speed 12 km/h, sights a 'ship B'. The velocity of B relative to A is 10Km/h in a direction of 270° . Find the magnitude and direction of the velocity of "ship B"