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1. Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

for this i have the answer of 36.4286m/s

assuming that is correct the question im stuck on is this

c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

force = mass x deceleration

deceleration = (45 - 36.4286) / 0.15 = 57.143

therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

help much appreciated
2. (Original post by lauren088)
Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

for this i have the answer of 36.4286m/s

assuming that is correct the question im stuck on is this

c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

force = mass x deceleration

deceleration = (45 - 36.4286) / 0.15 = 57.143

therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

help much appreciated
Draw two diagrams of the before and after collision with the initial velocity and final velocity, make sure if the car changes direction you appreciate the fact that if taking -> to be positive then <- would be negative. Use the conservation of momentum to determine the missing variable
Hint as there is a combined value of velocity, so you can just name the variable for both parts
You really need to show us the working to help you with each part
3. (Original post by lauren088)
Two vehicles travelling on a road in the same direction collide. Vehicle 1 has a mass 1200 kg and is travelling at 30m/s. Vehicle 2 has a mass 900 kg and is travelling at 45m/s. Assuming that the cars momentarily lock together and continue moving in the same direction determine the new velocity (combined) of the cars after the collision.

for this i have the answer of 36.4286m/s

assuming that is correct the question im stuck on is this

c)If the time of deceleration of vehicle 2 during the collision is 0.15 seconds determine the average force acting on this vehicle during this time.

force = mass x deceleration

deceleration = (45 - 36.4286) / 0.15 = 57.143

therefore force = 900 x 57.143 = 51428.7N ?????? IS THIS COMPLETELY WRONG ???

help much appreciated
It seems to be correct to me. Although the bit in bold should technically be (36.43-45)/0.15 to give you an acceleration of -57.1 m.s^-2 which is a deceleration of 57.1 m.s^-2 (remember a=(v-u)/t. But other than that, it all seems fine.

I would also leave the final answer to 3 significant figures so for the above F=51,400N

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