Q.

The position of a particle is given by r→=3ti^+2t2j^+5k^, where t is in seconds and the coefficients have the proper units for r→ to be in metres. The acceleration of the particle at t = 1 s is

1 2j^ m s-2  
2 -2j^ m s-2  
3 4j^ m s-2  
4 -4j^ m s-2  

Ans.

(3)

Given : r→=3ti^+2t2j^+5k^

Velocity, v→=dr→dt=ddt(3ti^+2t2j^+5k^)=3i^+4tj^ m s-1

 v→=3i^+4tj^ m s-1

∴  Acceleration, a→=dv→dt=4j^ m s-2

Acceleration of the particle remains constant all the time.