Physics Answers

Two identical balls, A and B, are released from rest from the same height, 2.8 m, along two smooth inclined planes that touch the horizontal ground. Ball A is released on a plane inclined at 30⁰ to the horizontal. The plane on which ball B is released is inclined at 60⁰ to the horizontal. Ignore energy due to rotation of the balls. [Diagrams, but no forces]

a) What is the speed of each ball at the bottom of their respective inclined planes?

b) Which ball would reach the bottom first? Explain your answer.

A 1,200 kg car ascends a road inclined at 20⁰ to the horizontal at 25 km/h. Neglecting frictional opposition, estimate the power required to keep going at this speed.

A power station delivers 25 MW of electrical power. How many tonnes of fuel oil would be needed by this station to deliver the 25 MW of power for 1 month of 30 days, assuming a conversion efficiency of 34%. (1 tonne of oil equivalent in energy = 4.2 X 10¹⁰ J, 1 tonne = 1,000 kg).

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Discuss two ways each in which fossil fuel energy can be conserved in Caribbean homes through:

a) measures involving reduced wastage of energy

b) sensible choice of equipment and appliances

c) making use of renewable energy.

It is planned to have replaced 20 MW output from a fossil fuel power station with a 20 MW output solar-voltaic power station. If the average solar insolation (power incident normally per square metre on the surface of the Earth) at a given location is 350 W m^-2, and the efficiency of the solar-voltaic cells is 20%, estimate the area of land surface required for generating the 20 MW of electrical power using solar-voltaic panels. 

Show that the sound wave intensity I can be written in terms

of the frequency f and displacement amplitude dm in the form, I = 2pi

vf ^2s^2 m.

A particle moves from x1 = 5 cm to x2 = 20 cm in 5 s. The average velocity of the particle during this time interval is

You are standing on a very slippery icy surface and throw a 1 kg football horizontally at a speed of 7.3 m/s. What is your velocity (in m/s) when you release the football? (Assume your mass is 66 kg and that the positive direction is the direction of motion of the football. Indicate the direction with the sign of your answer.)

An ice glider, that has a mass of 1640 kg, is initially moving at 20 m/s NW. A wind accelerates the glider at 2.5 m/s? 20° E of N for eight second. Then the wind shifts to 48°E of N accelerating the glider at 1.8 m/s for 11 seconds. 1) What is the glider's initial kinetic energy? 2) What is the glider's velocity at t= 8 s? 3) How much energy did the wind transfer to the glider during the 8 s? 4) What was the glider's velocity after the 11s the second wind gust was active? 5) How much energy did the wind transfer to the glider during the 19s? 6) What was the glider's average speed from t = 0 s to t = 19 s? 7) What was the glider's displacement from t = 0 s to t = 19 s? 8) What was the glider's average velocity from t = 8stot=198? 9) What was the glider's final kinetic energy? 10) A student contends that the glider will have the largest force at t = 19 s since it has the most kinetic energy at that time. Is this contention reasonable? Explain.