Question

1. A Light travels in a straight line at a constant speed of 300,000 km/s. calculate how far it will go in one millisecond.

2. which of the following statement is true and why?

A. speed can be negative

B. acceleration is always positive

C. constant speed implies constant velocity

D. acceleration and velocity always have the same direction

E. constant velocity implies constant speed

3. You have won the lottery. The prize is 20 lb of gold. Approximately how much is it worth, if 1 kg of gold is about $32,000.

Answer 1

1) Speed of light, v=300000 km/s

v=3×10^8 m/s

Time t=1 millisecond

t=1×10^-3 s

Distance travelled, d=vt

d= 3×10^8 ×1×10^-3

d= 3×10^5 m

d=300km

(2) (A) Speed can not be negative. Velocity can be negative or positive. Therefore, False.

(B) Acceleration can be negative or positive. Hence this statement is False.

(C) Velocity is vector quantity with magnitude and direction. Speed is scalar quantity with just the magnitude. Hence constant velocity does not mean constant speed. For example an object moving in uniform circular motion do have constant speed but velocity keeps on changing because of the direction.Therefore false.

(D) Acceleration and velocity can have same or different directions. Their directions need bot to be same. Therefore False statement.

(E) constant velocity will have the same magnitude. Hence speed will be the same as that of magnitude of the velocity. Hence this statement is True.