Physics Answers

The driver of a 2.0  × 103 kg red car traveling on the highway at 45m/s slams on his brakes to avoid striking a second yellow car in front of him, which had come to rest because of blocking ahead as shown in above Fig. After the brakes are applied, a constant friction force of 7.5 × 103 N acts on the car. Ignore air resistance.

(a) Determine the least distance should the brakes be applied to avoid a collision with the other vehicle? 

(b) If the distance between the vehicles is initially only 40.0 m, at what speed would the collision occur?

(c) Write your conclusive observations on the result obtained from this numerical. i.e. the importance of Physics in daily life.

The insulation resistance of a kilometer of the cable having a diameter of 2 cm and an insulation thickness of 2 cm is 600 ohms. If the thickness of the insulation is increased to 3 cm, find the insulation resistance of the cable.

The diameter of a given bare conductor is 0.50 inch. A thermoplastic insulation with thickness of 0.1 inch is wrapped around to insulate the conductor. Determine the insulation resistance of this conductor per meter. Assume specific resistance of thermoplastic insulation to be 2 x 1014 ohmcm.

A cylindrical rubber insulated cable has a diameter of 0.18 inch and an insulation thickness of 0.25 inch. If the specific resistance 0f rubber is 1014 ohm-cm, determine the insulation resistance per 1000 ft length of the cable.

Derive the equation a pentulam T.It depends on mass of the bob,length of the pentulam and acceleration due gravity?

Two heating elements which is 500 ohms and 250 ohms are connected in series with temperature coefficients of 0.001 and 0.003 ohms per °C, respectively at 20°C. Calculate the effective temperature coefficient of the combination.

It is required to construct a resistance of 100 Ω having a temperature coefficient of 0.001 per °C. Wires of two materials of suitable cross-sectional area are available. For material A, the resistance is 97 Ω per 100 meters and for material B, the resistance is 40 Ω per 100 meters. The temperature coefficient of resistance for material A is 0.003 per °C and for material B is 0.0005 per °C. Determine suitable lengths of wires of materials A and B.

A dc shunt motor after running for several hours on constant voltage mains of 400 V takes a field current of 1.6 A. If the temperature rise is known to be 40°C, what value of extra circuit resistance is required to adjust the field current to 1.6 A when starting from cold at 20°C? Temperature coefficient = 0.0043/°C at 20°C.

An armature has a resistance of 0.2 Ω at 150°C and the armature Cu loss is to be limited to 600 watts with a temperature rise of 55°C. If α0 for Cu is 0.0043/°C, what is the maximum current that can be passed through the armature?

A tungsten lamp filament has a temperature of 2,050°C and a resistance of 500 Ω when taking normal working current. Calculate the resistance of the filament when it has a temperature of 25°C. Temperature coefficient at 0°C is 0.005/°C