Question Set 70

1.Explain what is torque

Torque is the force that causes rotation. It is a measure of how much force is acting on an object making it rotate.

2.What is the difference between torque and power?

While power determines the speed of a vehicle, torque determines the time in which that speed can be reached. The greater the torque figure, the faster the acceleration. The more torque in the engine, the faster you accelerate. Power is the rate at which work is done, so it is basically the potential of the engine.

3.Explain why diesel engine is known as high torque and petrol engine as high speed engine?

Each power stroke in a petrol engine releases more heat and is converted into mechanical energy due to a higher rate of burning. This is the reason petrol engine has higher power and acceleration.

Diesel engine is a compression ignition engine with higher compression ratio, therefore extreme pressure is high. Since the piston of a diesel engine is larger, more torque is delivered in produced.

4.Why do heavy vehicles use diesel engine?

The compression ratio of diesel engine is higher than the petrol engine, the reason for producing higher torque. The efficiency of diesel engine increases with load. Diesel produces slow energy on burning of fuel and the efficiency of the engine increases with load which is why diesel engine is suitable and largely used for heavy vehicles.

5.Explain the difference between projectile motion and rocket motion.

The major difference is that a projectile has no motor or a rocket on it, due to which the momentum is given to it as it is launched. A pen thrown across a room is a classic example of a projectile motion. On the other hand, a rocket or missile has a motor on it which helps in accelerating while moving. This helps in resisting other forces such as gravity. A projectile does not have any specific shape, it is a point mass, whereas rocket has a particular shape having its center of gravity situated at a particular point on its body. Thus rocket motion comes under kinetics and projectile comes under kinematics.

6.Between steel, copper and brass, which conduct faster heat.

Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.

7.Explain the types of sensors.

(i) Temperature Sensor- This device collects information about the temperature from a source and converts it to a form which is understandable by another device or person. Glass thermometer is the best example where mercury acts as the temperature sensor.

(ii) IR Sensors- This device detects and/or emits infrared radiation to sense a particular phase in the environment. Mostly thermal radiation is emitted by all the objects in the infrared spectrum. This type of radiation is not visible to the human eye but the infrared sensor detects it.

(iii) UV Sensors- These sensors measure the intensity of the ultraviolet radiation. This form of electromagnetic radiation has wavelengths which are longer than x-rays yet shorter than visible radiation. UV sensors can discover the exposure of environment to ultraviolet radiation.

(iV) Touch Sensor- A touch sensor acts as a variable resistor based on the location where it is sensed. Proximity Sensor- A proximity sensor detects the presence of objects that are placed in close proximity without any point of contact.

8.What minerals are used in the manufacture of cars?

Cars are made from many various minerals. The steel body is made from the iron-rich minerals like magnetite and hematite. Door handles and badges are often coated in chromium which comes from chromite. Some of the other minerals used are aluminum, quartz, copper, magnesium, zinc, tin etc.

9.Which instrument measures speed in a car?

A speedometer helps measure the speed in the car.

10.What are the advantage and disadvantage of using LPG in a car?


The high octane rate enables it to blend better with air and to burn completely, generating less carbon. With less carbon buildup, spark plugs often last longer and oil changes are needed less frequently.

Since it burns in the gaseous phase, it results in less corrosion and engine wear.

In case of a spill, LPG evaporates quickly.


The LPG requires servicing at approximately once a year.

Since complete combustion occurs, more heat is liberated which is not advised for a long journey as the engine will get over heated.

Installation of LPG is rather difficult.

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