Borough of Manhattan Community College/CUNY, General Physics, PHY-110
Section: 521, Code: 3582. Instructor: Dr. Znamenskiy. Thursday, October 27, 2011. Midterm Exam
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1. Kinetic energy of the first body equals 20 Jules. The second body is moving with the speed which is twice higher then the speed of the first body, however the mass of the second body is twice lower than the mass of the firs body. What is the kinetic energy of the second body?
2. Potential energy of the first compressed spring equals 20 Jules. The second compressed spring has the spring coefficient twice higher, then the spring coefficient of the first spring, however the compression displacement of the second spring is twice lower the compression displacement of the first spring. What is the potential energy of the second compressed spring?
3. A tank holds 2 kL (kiloliters) of water.
a) How many kilograms of water is this?
b) What is weight of this water?
4. A car traveling in straight line with an initial velocity of 10 m/s accelerates at rate of 3m/s2 to a velocity of 22 m/s.
a) How much time does it take for the car to reach the velocity of 22 m/s?
b) What is the distance covered by the car in this acceleration process?
5. A cannon is fired over level ground at some angle to the horizontal. The vertical component of the initial velocity of the cannonball is 100 m/s and the horizontal component is 200 m/s.
a) How long is the cannonball in the air?
b) How far does the cannonball travel horizontally?
c) What is the maximum height reached by the cannonball?
6. A 50 kg crate is lowered from a loading dock to the floor using a rope passing over a fixed support. The rope exerts a constant upward force on the crate of 900N.
a) What are the magnitude and direction of the acceleration of the crate?
b) How fast is the crate traveling when it hits the floor if the height of the loading dock is 20m above the floor?
7. Two masses are attracted by a gravitational force of 450 N.
What will the force of attraction be if the distance between these two masses is tripled?
8. A car with a mass 500kg is traveling around a curve with a radius of 80 m
at a a constant speed of 20 m/s.
a) What is the magnitude of the centripetal acceleration of the car?
b) What is the magnitude of the centripetal force required to produce this acceleration?
9. Suppose that 100 g mass is oscillating at the end of spring upon a horizontal surface that is essentially friction free. The spring has a spring constant of 200 N/m. It was originally stretched a distance of 20 cm from its equilibrium (unscratched) position prior to release.
a) What is its initial potential energy?
b) What is the maximum speed that the mass will reach?
10. A 1000kg car traveling due north with a speed of 30 m/s collides head-on with a 2000kg truck traveling due west with a speed 20 m/s. The two vehicles stick together after the collision.
a) What is the total momentum of the system prior to the collision?
b) What are the speed of the two vehicles just after the collision?
c) What are the velocity of the two vehicles just after the collision?
11. A student, sitting on a stool rotating at a rate of 30 rev/min, holds masses in each hand. When his arms are extended, the total rotational inertia of the system is 8 kg·m2. He pulls his arms in close to his body, reducing the total rotational inertia to 4 kg·m2.
a) If there are no external torques, what is the new rotational velocity of the system in rev/min?
b) What is the new rotational velocity of the system in rad/s ?
12. A potter’s wheel, with rotational inertia 20 kg·m2 is spinning freely at 40 rpm The potter drops a lump of clay onto the wheel, where it sticks a distance 1 m from the rotational axis. If the subsequent angular speed of the wheel and clay is 20 rpm what is the mass of the clay?
13. A stream moving with a speed of 4 m/s reaches a point where the cross-sectional area of the steam decreases to one-fourth of the original area. What is the water speed in this narrowed portion of the stream?
14. The initial temperature of 300 g of ice is -40oC.The specific heat capacity of ice is 0.5 cal/(g·Co) and water’s is 1 cal/(g·Co). The latent heat of fusion of water is 80 cal/g.
a) How much heat is required to heat the ice to 0Co and completely melt the ice?
b) How much additional heat is required to heat the water (obtained by melting the ice) to 40oC?
15. The temperature of a beaker of water is 30oC.
a) What is this temperature in degrees Fahrenheit?
b) What is this temperature on the absolute (Kelvin) scale?
