Mechanics | Relativity Answers

The small piston of hydraulic lift has an area of 0.20 m2. A car weighing 1.20 x le N sits on a rack mounted on the large piston. The large piston has an area of 0.90 m2. How large a force must be applied to the small piston to support the car??

A football coach starts at the 10 yard line (A) and walks to the 40- yard line (B) in 3 minutes. He turns around and walks to the 0- yard line (C) in the next 2 minutes. He turns around again and walks back to the 50- yard line (D) in the next 3 minutes. He turns around once more and walks back to the 25 yard line (E) in the next two minutes, thus completing his 10 minute of pacing. The coach's overall displacement is

The velocity of the wind relative to the water is crucial to sailboats. Suppose a sailboat is in an ocean current that has a velocity of 2.01 m/s in a direction 25.1° east of north relative to the Earth. It encounters a wind that has a velocity of 4.93 m/s in a direction of 50.2° south of west relative to the Earth. What is the velocity of the wind relative to the water? (Enter the magnitude in m/s and the direction in degrees south of west.)

Water from a leaking tap begins to fall into an empty tank 0.5m wide by 2m long and 4m high. If the drops weigh 0.05g, after how many seconds will pressure be at the bottom of the tank be 200Pa ?

A football quarterback is moving straight backward at a speed of 1.71 m/s when he throws a pass to a player 21.1 m straight downfield. The ball is thrown at an angle of 40.3° relative to the ground and is caught at the same height as it is released. What is the initial velocity of the ball relative to the quarterback? (Assume downfield to be in the +x-direction. Enter the magnitude in m/s and the direction in degrees counterclockwise from the +x-axis.)

A ladder 7.85 m long leans against the side of a building. If the ladder is inclined at an angle of 66.5° to the horizontal, what is the horizontal distance from the bottom of the ladder to the building?

Why a baby wrapped tightly with warm cloths than an adult man in winter?

A swimmer wants to reach to a point just opposite on the bank of river. How should he swim and why?

A droplet of perspiration falls off a worker who is standing on a platform 40 m above the
ground. Assume throughout that the drop is spherical (volume of a sphere is equal to 4
3
πr3
while its surface area is equal to 4πr2
). Your objective is to investigate what happens to
the drop as it falls down.
(a) Suppose that as the drop falls, the droplet evaporates at a constant rate. If V is the
volume of the drop, this means that
dV
dt = −c,
where c is a positive constant. Find an expression for dr/dh, that is, the rate of change
of the droplet’s radius with respect to the height h above the ground. (3 marks)
(b) A more realistic model is to suppose instead that the rate of evaporation is proportional
to the surface area of the drop. Find dr/dh now. (3 marks)
(c) Is it possible, in either of these models, that the drop disappears via evaporation just
before hitting the ground?

3 Which of the following substances is ductile?
a. glass
b. high carbon steel
c. copper
d. brass

4 A solid cylindrical steel column is 4.0 m long and 9.0 cm in diameter. What will be its decrease in length when carrying a load of 80 000 kg? Y=1.9×1011PA
a. 5.2 mm
b. 1.4 mm
c. 3.7 mm
d. 2.6 mm