Mechanics | Relativity Answers

1. An arrow accelerates from 0 to 40 m/s in the 0.5 s it is in contact with the bow string. What is the average acceleration?

2. A coastal force of 20 N acts on a mass of (a) 2 kg, (b) 4 kg, (c) 6 kg. What are the resulting acceleration?

3. A 0.5 kg wrench is dropped from a height of 10 m. What is the momentum just before it strikes the floor?

An iron ball of mass 3\,\,kg3kg is hanging at rest tied to the roof by a vertical massless string of length 10m. Then a horizontal force F=14\,\,NF=14N acts on the ball till the ball reaches a point where the string makes an angle of 37 with the vertical. Find the speed of the ball at this instant. (Assume g=10m/s2 sin37=0.6 )

At the top of trajectory ,a mortar shell explodes into two fragments ;a 2.5kg pieces moves south west with a horizontal velocity of 100m/s while 3.5kg piece moves north with a horizontal velocity of 70 m/s.what was the horizontal direction of the cell just before explosion

kangaroos are good runners that can sustain a speed of 56 km/h (15.5 m/s). suppose a kangaroo is sitting on a log that is floating in a lake. when the kangaroo gets scared, she jumps off the log with a velocity of 15 m/s toward the bank. the log moves with a velocity of 3.8 m/s away from the bank. if the mass of the log is 250 kg, what is the mass of the kangaroo?

a 1.75 kg stone falls from the top of a cliff and strikes the ground at a speed of 58.8
m/s. what is the height of the cliff?

Complete the wavelength of the light of the following and comment on what will happen to the light in these scenarios:
a) Light passes through two slits 2.7 micrometers apart and shines on a screen. The first order maxima occurs at angle 9.5 degrees.
b) Light is incident on a metal with work function 2.28eV. The maximum kinetic energy of photoelectrons is 0.51eV.

Compare and contrast properties of waves and particles, explaining which properties can and cannot distinguish between wave-like behaviour and particle-like behaviour.

A 15m wide horizontal platform is suspended by ropes at each end, each capsule of withstanding tension of 112KN. The uniform concrete platform has mass 1500kg.
a) Calculate the maximum load that can be added to the centre of the platform
b) Calculate the maximum load that can be added to the extreme ends of the platform
c) Explain why these two calculations produce different values
d) Suggest a value for the maximum safe recommended load for the platform and justify

An alloy of steel has a Young's modulus of 180GPa, elastic limit of 0.002 and ultimate tensile strength of 860MPa. An alloy of aluminium has a Young's modulus of 70GPa, elastic limit of 0.004 and ultimate tensile strength of 110MPa.
a) Sketch a stress-strain graph for both of these alloys, plotting them on the same graph
b) Label significant positions on the graphs
c) Compare and contrast the mechanical properties of these alloys

A 15m wide horizontal platform is suspended by ropes at each end, each capsule of withstanding tension of 112KN. The uniform concrete platform has mass 1500kg.
a) Calculate the maximum load that can be added to the centre of the platform
b) Calculate the maximum load that can be added to the extreme ends of the platform
c) Explain why these two calculations produce different values
d) Suggest a value for the maximum safe recommended load for the platform and justify