After a glass rod is rubbed with a nylon cloth
A. both the rod and cloth will have a positive charge.
B. the rod will have a negative charge and the cloth positive.
C. both the rod and cloth will have a negative charge.
D. the rod will have a positive charge and the cloth negative.
E. the rod will have a negative charge and the cloth will be neutral.
Answer: D
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A spaceship moves at a speed of 0.95 c away from the Earth. It shoots a star wars torpedo toward the Earth at a speed of 0.90 c relative to the ship. What is the velocity of the torpedo relative to the Earth? (The direction in which the spaceship moves is the positive direction.)
a. ?0.34 c b. 0.34 c c. 0.060 c d. ?0.060 c e. 0
A force is required for an object to accelerate
Indicate whether the statement is true or false
A spherical stainless steel vessel at 93°C contains 45 kg of water initially at the same temperature. If the entire system is suddenly immersed in ice water, determine (a) the time required for the water in the vessel to cool to 16°C, and (b) the temperature of the walls of the vessel at that time. Assume that the heat transfer coefficient at the inner surface is 17 W/(m2 K), the heat transfer coefficient at the outer surface is 22.7 W/(m2 K), and the wall of the vessel is 2.5-cm-thick.
GIVEN
• A spherical stainless steel vessel of water is suddenly immersed in ice water
• Initial temperature of vessel and water (Ti) = 93°C
• Mass of water in the vessel (m) = 45 kg
• The inner heat transfer coefficient ci h = 17 W/(m2 K)
• The outer heat transfer coefficient co h = 22.7 W/(m2 K)
• The vessel wall thickness (L) = 2.5 cm = 0.025 m
FIND
(a) The time required for the water in the vessel to cool to 16°C (b) The temperature of the walls of the vessel at that time (Tsf)
ASSUMPTIONS
• The water in the vessel is well mixed, therefore its temperature is uniform
• The vessel is completely filled with water
SKETCH
Which spacecraft launched a probe that smashed into comet Tempel 1?
A. NEAR B. Deep Impact C. Hayabusa D. Stardust