Question

Two objects of masses 3 kg and 6 kg are moving with the same

momentum of 30 kgms​-1.

(i) Will they have the same kinetic energy?

(ii) Will they have the same speed? Prove it.

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Answer 1

(i) Given

M1 = 3 kg

M2 = 6 kg

P = 30 kgm/s

v1 = ?

v2 = ?

We know that

P = mv

=> 30 = 3×v1

=> v = 10 m/s

Now, We find v2

=> 30 = 6×v2

=> v2 = 5 m/s

Acording to the Ans.

We know that

K.E. = 1/2mv^2

=> K.E.1 = 1/2×3(10)^2

=> K.E.1 = 1/2×3×100

=> K.E.1 = 150 J

Now, we find value of K.E.2

=> K.E.2 = 1/2×6×(5)^2

=> K.E.2 = 1/2×6×25

=> K.E.2 = 75 J

Hence, they have different Kinetic Energy.

(ii) No They not have same velocity. Already Proved in part (i).