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A towing van of mass 6.0 * 10^3 kg used in towing a car of mass m moved with a speed of 4ms^-1 just before the towing rope become taut. Calculate the(i) value of m if the speed of the van reduced to 2.5 ms^-1 when the rope became taut.(ii) loss in kinetic energy of the system after the car had started moving.(iii) impulse in the rope when it jerked the car into motion.I don't know what principle to apply in solving the problem. Somebody help me please.

Impulse = change in momentum of the carImpulse = Mcv - McU= 3600*2.5 - 3600*0= 9000 Ns. What do you have to say cocerning my works?

In the first place I congradulate you on desire to learn physics. It's well known to be the hardest thing on earth to master. Second, there is insufficient information to solve all but the mass of the car, which you did correctly. I recommend that the next time you first leave all the variables in until you do the final calculation. E.g. If M - mass of truck and m = mass of car, v_initial is the initial speed of truck and v_final is the final speed of the truck-car system then the mass of the car is m =(v_initial/v_final - 1)M = (4/2.5 - 1)6x10^{3}kg = 3.6x10^{3}kg.You made an error in your calculation of kinetic energy loss. Please recheck your calculation. Since energy is a conserved quantity do you know where the kinetic energy went to?The value for the impulse seems okay to me.

I can hardly see any error in my calculation of kinetic energy loss.

.. because part of the kinetic energy has been dispensed in towing the car.

Quote from: ChikisI can hardly see any error in my calculation of kinetic energy loss.You calculated the final kinetic energy to be 30000J but when you went to subtract it froom the initial kinetic energy of 48000 you mistakenly used 3000J leaving off a "0".Quote from: Chikis.. because part of the kinetic energy has been dispensed in towing the car.The missing energy went into thermal energy and energy of deformation.

The missing energy went into thermal energy and energy of deformation.

Do you mean the missing enery was used as energy of the deformation of the rope? What themal energy are you making refrence to? Thank you.

Quote from: Chikis on 10/08/2013 03:13:49A towing van of mass 6.0 * 10^3 kg used in towing a car of mass m moved with a speed of 4ms^-1 just before the towing rope become taut. Calculate the(i) value of m if the speed of the van reduced to 2.5 ms^-1 when the rope became taut.(ii) loss in kinetic energy of the system after the car had started moving.(iii) impulse in the rope when it jerked the car into motion.I don't know what principle to apply in solving the problem. Somebody help me please.It depends what reference frame you're in