Q.

A force defined by F=αt2+βt acts on a particle at a given time t. The factor which is dimensionless, if α and β are constants, is             [2024]

1 βtα  
2 αtβ  
3 αβt  
4 αβt  

Ans.

(2)

F=αt2+βt

Dimension of α=[MLT-2][T2]=[MLT-4]

Dimension of β=[MLT-2][T]=[MLT-3]

Option a): βtα=[MLT-3][T][MLT-4]=[M0L0T2]

Option b): αtβ=[MLT-4][T][MLT-3]=[M0L0T0]

Option c): αβt=[MLT-4][MLT-3][T]=[M2L2T-6]

Option d): αβt=[MLT-4][MLT-3][T]=[M2L2T-8]

Hence, option (b) is correct.