Mechanics | Relativity Answers

An 80N wooden block is placed on top of a wooden table. If a force of 28N is necessary to keep the block moving at a constant velocity. (a) What is the coefficient of sliding friction for the block & table. (b) If a weight of 40N is paced on top of the wooden block. What force will be required to keep the block and weight moving at a constant velocity across the table?

A PARACHUTIST BAILS OUT AND FREELY FALLS 50M THEN THE PARACHUTE OPENS , AND THEREAFTER SHE DECELERATES AT 2M/S². SHE REACHES THE GROUND WITH A SPEED OF 3M/S.
1.) HOW LONG WAS THE PARACHUTE IN THE AIR?
2.) AT WHAT HEIGHT DID THE FALL BEGIN?

A man of mass 80 kg is standing stationary in the middle of a train
carriage (see the figure below). The train is moving horizontally with a constant speed of
20 m/s (see the figure below), and the carriage is L = 20 m long. Suddenly, the train starts to accelerate uniformly with a = 2 m/s2 horizontally.
(a) Is the reference frame of the train now an inertial frame? Design an experiment that
allows you to find out.
(b) Draw a free-body diagram of the man. Label the forces appropriately and explain
their physical origin (one line each will suffice).
(c) If the coefficient of friction between the man’s shoes and the ‘floor’ of the train is
µ = 0.1, what is the maximum time that the man takes to hit the back of the train
carriage? For simplicity, you can assume that the coefficient of static friction is the
same as the coefficient of kinetic friction. Assume that there are no obstacles between
the man and the back of the train.

Describe one "Newton's third law pair" of force involved in the following situations. In each case, state the object each force acts on. the type and direction of the force.
(a) you step on someone's toe
(b) a car hits a brick wall and comes to rest.
(c) a car slow down by applying the brakes.
(d) you throw a ball upward into the air.

(1)
A parachutist weighs 100N. When she opens her parachute, it pull upward on her with a force of 200N.
(a) draw a diagram to show the forces acting on the parachutist.
(b) calculate the resultant forces acting on the parachutist
(c) what effect will this forces have on her?

A trolley of mass 4kg moving on smooth horizontal platform with a speed of 1.0m\s collide perfectly with a stationary trolley of same mass in the same platform. Calculate in total momentum of the two trolley immediately after the collision

The forces of 10N and 20N are in plain at an angle 60⁰ to each other. Find the resultant and the direction using
1. Analytical method
2. Scle drawing method

A wire of length 2m and radius 2mm is fixed to the center of wheel a torque of magnitude 0.0395Nm is applied to twist the wire find the regidity modulus of wire if angular twist is 0.038radian

An 80 kg patient went to a doctor . The doctor advised him to reduce his weight. Should the patient
plan to live on the moon so that his weight gets reduced? Explain your answer.

The mass (in kg), position coordinates (in m) and velocity (in m s−1) of a system of three particles A, B and C are as follows: Particle Mass A B C 2.0 kg 1.0 kg 3.0 kg Position (0, 0) (2, 0) (1, 1) Velocity r 0 4.0ˆ j 2.0ˆ

Find or calculate the acceleration of drag car that goes from 0 to 300km/h in 0.56km.