Mechanics | Relativity Answers

A particle with velocity v0= -2i+4j in meters per second at t=0 undergoes a constant acceleration a of magnitude a=3ms^-2 at an angle =130° from the positive direction of the x axis. What is the particles velocity v at t=5s, in unit vector notation and as a magnitude and an angle?

This circular railroad crossing sign has a diameter of 1.3 m. The distance from the bottom of the sign to the ground is 3m. Determine the moment at the base 'A' of the sign due to the wind drag on the front of the sign. Wind speed is 150 kilometer per hour. Air temperature 20 degree celsius. Neglect the drag on the pole.

Q9 : A car covers 300 m in 20 seconds, while accelerating
uniformly at a rate of 5m/s2. Determine :
(i) Initial and final velocities of the car
(ii) Distance travelled before coming to this point assuming it started
from rest
(iii) Its velocity after the next 10 seconds. Q10 : A tennis ball traveling at 25.0 m/s is returned by Williams. It
leaves his racket with a speed of 39.0 m/s in the opposite direction from
which it came. i) Calculate the change in momentum of the tennis ball.
ii) If the 0.080 kg ball is in contact with the racket for 0.020 s,
calculate the average force needed for Williams to hit the ball.
iii) As a Safety Officer predict what happens if the mass of the ball
increases.

Q5: Determine, by resolution of forces, the resultant of
the following three coplanar forces acting at a point:
12 kN acting at 32° to the horizontal; 25 kN acting at
170° to the horizontal; 40 kN acting at 240° to the
horizontal
Q6: Determine by resolution of forces the resultant of
the following three coplanar forces acting at a point:
300N acting at 20° to the horizontal; 500N acting at
165° to the horizontal; 600N acting at 250° to the
horizontal.

Determine graphically the magnitude and direction of the
resultant of the coplanar forces given which are acting at a
point.
Q3: Force A, 35N acting horizontally to the right, force B,
15N acting at 160° to force A; force C, 18N acting at 280°
to force A.
Q4: Force 1, 23 kN acting at 60° to the horizontal, force 2,
30 kN acting at 32° to force 1, force 3, 25 kN acting at 70°
to force 2.

Q1: Use the parallelogram of forces method to find the
magnitude and direction of the resultant of a force of 20N
acting at an angle of 156° and a force of 34N acting at an
angle of 243o Q2: Determine the magnitude and direction of the resultant
of a force of 15N acting horizontally to the right and a force
of 20N, inclined at an angle of 60° to the 15N force. Use
the triangle of forces method.

An electric train starting from rest attains a maximum
speed of 200 kmph in 20 seconds. Determine :
(i) Its acceleration assuming it to be uniform
(ii) Distance covered during this time period
(iii) Its velocity 15 seconds after staring from rest

An airplane while taking off moves with a constant
acceleration over a runway of 600 m in 10 seconds.
Determine the velocity with which it takes off. Also,
determine its constant acceleration.

A student was asked to stack up uniform blocks each
measuring 25.0 cm long and 3.25 cm thick so that
alternately 2.5 cm and 5.0 cm extended beyond the block
beneath. How many blocks can be stacked before the stack
falls over? How high is the center of gravity of the last stack
that will not fall over?

A tall man with a red tie is riding up in an elevator. He realizes that he is standing on a scale, which reads 700N, while the elevator is at rest. When the elevator begins to move, the scale reads 476N. a) Determine the acceleration of the elevator. b) How long will it take to reach 10m/s?