Physics Answers

Two bodies of masses 10kg and 4kg are moving in opposite directions with the same velocity of 5 meter per seconds .if they collide and stick together after the impact,calculate their velocity

The resistance of a wire of length 100cm diameter 0.3mm is found to be 3.0 ohms Calculate (1) the resistivity (2) the conductivity of the material of a wire

1. Salim has a paper route. In the winter time, he puts his newspapers on a toboggan to pull them through the snow. The combined mass of the papers and the toboggan is 24 kg. The coefficient of static friction between the toboggan and the snow is 0.18. The coefficient of kinetic friction between the toboggan and the snow is 0.10.
2. With how much force must Salim pull in order to get the toboggan to start moving?
3. How much force is needed to keep the toboggan moving at a constant speed?

A bucket full of water and weighing 200N is supported by two men holding the handle at each side, each pulling sideways at an angle of 30° to the vertical. Find the force in each man's arm.

Calculate the average acceleration needed by a train travelling initially at 12m/s[E] to stop in 120s.

1. A resistor with resistance R = 30 MΩ is connected in series with a capacitor with capacitance 3 μF. What is the

time constant?

2. Determine the equivalent (total) resistance for each of the following circuits below.

1. Why do lights on a car become dimmer when you start a car?

2. Some Christmas tree lights have a characteristic that when one light (filament) burns out, the lights throughout go

out too. However, burned-out lights go out in other series lights. Discuss the difference between these two sets of

lights.

1. Find the current density and drift velocity of free electrons when the particles travel on a copper conductor with a square cross-section of 1.0 mm on the side and carries a current of 40 A to a 5 hp electric meter and its density of 6.0 x 1028 electrons/m3

2. Suppose the resistance is 1.47 Ω at a temperature of 20°C. Find the resistance at 0 degree Celsius.

1. How would you expect the resistivity of a good insulator such as glass or polystyrene to vary with temperature?

2. A fuse is a device that is designed to break the circuit. It melts when the current exceeds its value. What

characteristics should the material have?

1. The potential energy of a certain system of two charges increases as the charges are moved farther apart. What does

this tell us about the sign of the charges? Why?

2. Show that volt per meter is the same as newton per coulomb.

3. A student said "electric potential is always proportional to potential energy; why bother with the concept of potential at

all? How would you respond?