1- A man pulling an empty wagon causes it to accelerate at 2 m/s2. What will the
ID: 1657745 • Letter: 1
Question
1- A man pulling an empty wagon causes it to accelerate at 2 m/s2. What will the acceleration be if he pulls with the same force when the wagon contains a child whose mass is 7 times that of the wagon?
2- A 1,302 kg car is traveling along a straight; road at 14 m/s. 6 seconds later its speed is 20 m/s. What is the magnitude of the net force acting on the car during this time?
3- Squid use jet propulsion for rapid escapes. A squid pulls water into its body and then rapidly ejects the water backward to propel itself forward. A 1.7 kg squid (not including water mass) can accelerate at 21 m/s2by ejecting 0.16 kg of water. What acceleration (magnitude) is experienced by the water?
4- A car has a mass of 2,250 kg. If the driver applies the brakes while on a gravel road, the maximum friction force that the tires can provide without skidding is about 7,500 N . If the car is moving at 15 m/s, what is the shortest distance in which the car can sstop safeIy?
Explanation / Answer
1. accelaratio of the wagon aw = 2m/s2
Let the mass of the wagon is m
foce on the wagon F = 2m N
Mass of the boy M = 7m
force on the child F = 7m x a
hence 2m = 7m a
accelaration a = 2/7 = 0.285 m/s2
2. Mass of the car m = 1302 kg
accelaration a = ( v - u ) / t
= ( 20 - 14 )/6
= 1 m/s2
Net force on car F = m a = 1302 x 1 = 1302 N
3. Mass of squid M = 1.7 Kg
accelaration of squid as = 21 m/s2
force F = m x a = 1.7 x 21 = 35.7 N
mass of water m = 0.16m/s2
accelaration of water a = F/m 35.7/0.16 =223.12 m/s2
4. mass of the car m = 2250 Kg
frictional force F = 7500 N
accelaratio a = F/m = 7500/2250 = - 3.33 m/s2
using the relation v2 = u2 + 2.a.s
0 = u2 - 2.a.s
required distance s = u2 / 2a = 15 x 15 / 2 x 3.33
= 225/6.66
= 33.8 m
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