Question

Science - IX
Motion (Assignment 1)
1. The minute hand of a clock is 7 cm long. Calculate the distance covered and the displacement of timute hand
of the clock from 9.00 AM to 9.30 AM.
Ans: 14 cm
2. An athlete completes a round of a circular track of diameter 200 m in 20 s. Calculate Ans: €) 2200 (i) 200 ml​

Answer 1

Solution:

1. Visualize the clock as a circle.

Minute hand of the clock=Radius of clock=7cm

The region between 9:00 and 9:30 is a semicircle.

The base of this semicircle is the line that joins 9:00 and 9:30 i.e., diameter

Now,

Diameter

=2radius

=2(7)

=14cm

2. From the question,

Time taken:20s

Diameter:200m

Radius:100m

Distance covered: Circumference

Distance:2πr

=2(3.14)(100)

=6.28(100)

=628m

Speed:

Distance/Time

=628/20

=314/10

=31.4m/s

Displacement:2r=2(100)=200m

Velocity:

Displacement/Time

=200/20

=10m/s