Question

A man rode a distance of 61 miles in 7hrs for part of the time he rod at 8mph and tbe rest he rode at 10 mph for how long did he ride of 8mph.?

Answer 1

Answer:

The term "the collision is perfectly elastic" means that after the collision the masses remain the same

and both the momentum law and conservation of mechanical energy are held.

If v%5B1%5D and v%5B2%5D are the velocities of the particles after the collision, then the momentum conservation equation is

2 kg * 1 m/s + 1 kg * 0 m/s = 2%2Av%5B1%5D + 1%2Av%5B2%5D,

Left side is the momentum value BEFORE the collision; right side is that AFTER the collision. In the short form

2%2Av%5B1%5D + v%5B2%5D = 2 (kilogram*meter/s). (1)

The mechanical energy conservation equation is

%282%2A2%5E2%29%2F2 + %281%2A0%5E2%29%2F2 = %282%2Av%5B1%5D%5E2%29%2F2 + %281%2Av%5B2%5D%5E2%29%2F2.

Left side is the kinetic energy value BEFORE the collision; right side is that AFTER the collision. In the short form

%282%2Av%5B1%5D%5E2%29%2F2 + %28v%5B2%5D%5E2%29%2F2 = 4 (kg*m^2/s^2, or joules). (2)

Answer 2

If a man rode a distance of 61 miles in 7 hrs for part of the time he rod at 8 mph and the rest he rode at 10 mph then he rode of 8 mph for 4.5 hrs.

Step-by-step explanation:

Required formula:

Distance = Speed * Time

Total distance = 61 miles  

Total time taken to ride a distance of 61 miles = 7 hrs

So, let the time for which the man rode at a speed of 8 mph be “t” hr  

Then the time for which the man rode at a speed of 10 mph be “(7 – t)” hr

According to the question, we can write the equation as,

[8 * t] + [10 * (7-t)] = 61  

⇒ 8t + 70 – 10t = 61

⇒ 2t = 9

⇒ t = 4.5 hrs

Thus, for 4.5 hours he rode at a speed of 8 mph.