PHY101 Solution of Assignment 1

Q # 2

A spaceship is moving in the vacuum of outer space, far from any planet, when its engine dies. As a result, the spaceship slows down and stops. What does Newton‘s first law say about this event? Marks = 5

Solution:-

In this situation there are no forces acting on the spaceship, so according to Newton’s first law, it will not stop. It continues to move in a straight line with constant speed, some science fiction movies have made use of very accurate science; this was not one of them.

Q # 1

Consider a box that is placed on different surfaces. Marks = 10

a) In which situation (s) is there no force acting on the box?
b) In which situation (s) is there a static friction force acting on the box?
c) In which situation (s) is there a kinetic friction force acting on the box?
Various possible situations are as under:
I. The box is at rest on a rough horizontal surface.
II. The box is at rest on a rough tilted surface.
III. The box is on the rough-surfaced flat bed of a truck- the truck is moving at a
constant velocity on a straight, level road and the box remains in the same
place in the middle of the truck bed.
IV. The box is on the rough-surfaced flat bed of a truck- the truck is speeding up
on a straight, level road, and box remains in the same place in the middle of
the truck bed.
V. The box is on the rough-surfaced flat bed of a truck- the truck is climbing a
hill, and the box is sliding towards the back of the truck.

Q # 3
A traffic light of weight W hangs from two light cables; one on each side of the light.
Each cable hangs at a 450 angle from the horizontal. What I the tension in each cable?
Marks = 5