Question

1. A train travelling at 20 m s-1 accelerates at 0.5 m s-2 for 30 s.
How far will it travel in this time.
2. A cyclist is travelling at 15 m s-1 . She applied break so that she does not collide with a wall 18 m away. What desolation must she have ?

Answer 1

1)
velocity v=20m/s
acceleration a =0.5m/s²
time t=30s
let distance travel =S
using Newton law of motion,
S=ut+1/2at²
S=20x30+0.5x(30)²/2
S=600+0.5x900/2
S=600+0.5x450
S=600+225
S=825m
Hence, distance travelled is 825 metres .
2)
initial velocity u=15m/s
final velocity v=0m/s. (brake is applied)
distance S=18m
let retardation =a m/s²
using Newton law of motion,
V²-u²=2aS
a=V²-u²/2S
a=0-(15)²/2x18
a=-225/36
a=-6.25m/s²
Hence, retardation is 6.25m/s².