Name: Examples of Non-contact Forces
Uploaded: 2019-07-19
Duration: 3 min 24 s
Description: Can two objects apply force on each other without coming in physical contact? Can you push a door without touching it? Let's explore in this video.

Question

The velocity of a body of mass

50 kg

moving at a uniform acceleration becomes

7 m s^{- 1}

from

4 m s^{- 1}

in

6 \sec

. Calculate the initial and final momentum of the body and the force applied on it.

Accepted Answer

Given that,
Mass of the body is $50 kg$
Initial velocity of the body is $u = 4 m s^{- 1}$
Final velocity of the body is $v = 7 m s^{- 1}$
Time taken is $∆ t = 6 s$
We know that, momentum $(p)$ $=$ mass $(m)$ $\times$ velocity $(v)$
Initial momentum $p_{i} = m u = 50 \times 4 = 200 kg m s^{- 1}$
Final momentum $p_{f} = m v = 50 \times 7 = 350 kg m s^{- 1}$
We also know that, rate of change of momentum is directly proportional to the force.
$F = \frac{∆ p}{∆ t} = \frac{p_{f} - p_{i}}{∆ t} = \frac{350 - 200}{6} = 25 N$
Hence, the force applied on the body is $25 N$ .

The velocity of a body of mass $50 kg$ moving at a uniform acceleration becomes $7 m s^{- 1}$ from $4 m s^{- 1}$ in $6 \sec$ . Calculate the initial and final momentum of the body and the force applied on it.

Important Questions on Force and Laws of Motion

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