Mechanics | Relativity Answers

Boston Red Sox pitcher Roger Clemens could routinely throw a fast ball at a horizontal speed of 160 km. How long did the ball take to reach home plate 18.4m away? 

(a) Derive the formula for elastic potential energy, PEE, in terms of applied force F, stiffness constant k, and extension ΔL of a wire. State any assumptions made. (b) Figure 4.6a shows a F versus ΔL graph for a wire of length 2.0 m and diameter 1.2 mm. (i) Determine the stiffness constant of the wire from the graph. (ii) Determine the Young’s modulus for the material of the wire. (iii)What is a practical advantage of knowing the Young’s modulus as compared with the stiffness constant of the wire?

(a) Outline problems involved in the large-scale use of photo-voltaic electricity in terms of availability of solar energy and that a large area is required to capture adequate amounts of solar energy. (b) It is planned to replace a 20 MW output fossil fuel power station with a 20 MW output solar-voltaic power station. If the average solar insolation (power incident normally per square meter 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. 

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 30° to the horizontal. The plane on which ball B is released is inclined at 60° to the horizontal. Ignore energy due to rotation of the balls. (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.

2. An object of mass 10 kg is whirled round a horizontal circle of radius 4 m by a revolving string inclined to the vertical. If the uniform speed of the object is 5 m/s, calculate:

(i) the tension in the string

(ii) the angle of inclination of the string to the vertical.

Find the sum of A = 3i + 4j -5K and B = -i + 2j +6z

Suppose that two objects attract each other with force of 16 units. If the distance between the two objects is doubled, what is the new force of attraction between the two objects

At what distance must two equal sphere be place so that the force of attraction between them would be 3.35×10-6N if the mass of the sphere is 90kg each

determine the average gravitational force between a 1.05 solar mass and a planet whose orbital speed is 20,000 m/s if its distance from the star is 149 million kilometers at its nearest and 150 million kilometers at its farthest.

A car travels 100m as it accelerates from rest at 25m/s. Calculate the acceleration.