# NCERT Class 11 Physics Solutions: Chapter 3 – Motion in a Straight Line Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question: 3.5

A jet airplane travelling at the speed of ejects its products of combustion at the speed of relative to the jet plane. What is the speed of the latter with respect to an observer on ground?

Answer:

• Speed of the jet airplane,
• Relative speed of its products of combustion with respect to the plane,

• Speed of its products of combustion with respect to the ground smoke
• Relative speed of its products of combustion with respect to the airplane,

• The negative sign indicates that the direction of its products of combustion is opposite to the direction of motion of the jet airplane.

Question: 3.6

A car moving along a straight highway with a speed of is brought to a stop within a distance of . What is the retardation of the car (assumed uniform) , and how long does it take for the car to stop?

Answer:

• Initial velocity of the car,
• Final velocity of the car,
• Distance covered by the car before coming to rest,
• Retardation produced in the car
• From third equation of motion, a can be calculated as:

• From first equation of motion, time (t) taken by the car to stop can be obtained as:

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