www.bbcnoun.com.ng PHY101 7/10 1. The displacement of a particle from a reference point at any instant is given by s=3t2-4t+5, where s is in metres and t is time in seconds. Calculate the average velocity of the particle in the time interval between 3 s and 5 s, and its instantaneous velocity at 4 s. v-=20 ms-1 and v=20 ms-1 2. How much heat is transferred in 1 hour by the process conduction through a concrete wall 2 m high, 3.65 m long and 0.2 m thick if one side of the wall is held at 20 °C and the other side at 5.0 °C? [Take the thermal conductivity of concrete as 1.3×10-6 Wm-1°C-1]. 2.6×106 J 3. If a?=3i^-2j^-k^ and b?=i^+4j^+k^, find a unit vector n^ normal to the plane containing a? and b? such that a?, b? and n^, in this order, form a right-handed system. n^=15j^-25k^ 4. Calculate the direction cosines of a?+b?, given that a?=4i^+7j^-5k^ and b?=3i^+4j^+k^ l=7186, m=11186 and n=-4186 5. A copper block of mass 0.75 g is removed from a furnace and quickly transferred into a glass beaker of mass 300.0 g containing 200.0 g of water. The temperature of the water rises from 12.0 °C to 27.0 °C. What was the temperature of the furnace? 530.0 °C 6. a = 0, b =12 , c = -12 7. A certain resistance thermometer reads 14.5 O in pure melting ice and 18.5 O in steam at standard atmospheric pressure. What will be its resistance at room temperature of 27.0oC? 15.58 O 8. A piece of metal has a mass of 200 g in air and 170 g when immersed in water. Calculate its volume and density. [Density of water is 1000 kgm-3. Take g=9.8 ms-2 ] 3.0×10-5 m-3, 6.67×103 kgm-3 9. x'=x; y'=y; z'=z-vt; t'=t 10. P=3.25×107 W; 0.35 °C