# Velocity, Acceleration and Force

1. A body with initial velocity 8.0 m/s moves along a straight line with constant acceleration and travels 640 m in 40 s. For the 40 s interval, find (a) the average velocity, (b) the final velocity, and (c) the acceleration.

2. A mass of 10 kg is hanging from a spring scale that is in turn hanging from a hook attached to the ceiling. The scale indicates a reading of 98 N for the force. Then two people hold the spring scale horizontally and pull on opposite ends until the scale again reads 98 N. With what force must each person pull to attain this result?

3. A train running along a straight track at 30 m/s is slowed uniformly to a stop in 44 s. Find the acceleration and the stopping distance.

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A body with initial velocity 8.0 m/s moves along a straight line with constant acceleration and travels 640 m in 40 s. For the 40 s interval, find (a) the average velocity, (b) the final velocity, and (c) the acceleration.

Solution:

S=ut+1/2 at^2

Or,640m=8m/sÃ—40s+1/2 aã€–(40s)ã€—^2

Or,a=0.4m/s^2

Therefore, acceleration = 0.4m/s2

Final Velocity,v=u+at=(8+0.4Ã—40)m/s=24m/s

Average Velocity =

640m/40s=16m/s

A mass of 10 kg is hanging from a spring scale that is in turn hanging from a hook attached to the ceiling. The scale indicates a reading of 98 N for the force. Then two people hold the spring scale horizontally and pull on opposite ends until the scale again reads 98 N. With what force must each person pull to attain this result?

Solution: Each person should exert a force equal to

98N/2=49N

A train running along a straight track at 30 m/s is slowed uniformly to a stop in 44 s. Find the acceleration and the stopping distance.

Solution:

v=u+at

Or,a=(v-u)/t=(0-30)/44 m/s^2=-0.68m/s^2

The negative sign indicates retardation.

Stopping Distance,S=ut+1/2 at^2=30Ã—44-1/2Ã—0.68Ã—ã€–44ã€—^2 m=661.76m

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