First slide

Work

Question

A 2kg block is pulled upwards by 60N force. The ratio of magnitudes of total work done and work done against gravity after 3 seconds ${(g=10ms}^{- 2})$

Moderate

A

2:1
B

3:2
C

2:3
D

3:4

Solution

$\begin{array}{l} Vet work done = W_{f} + W_{g} \\ = W_{f} + W_{g} \\ W = F . S C O S 0 + mgs \cos 180 \\ = 60 \times \frac{1}{2} a t^{2} \times 1 + 2 \times 10 \times \frac{1}{2} a t^{2} \times (- 1) (∵ a = \frac{F - m g}{m}) \\ = 30 \times (\frac{60 - 20}{2}) \times 9 - 10 \times (\frac{60 - 20}{2}) \times 9 \\ = 20 \times \frac{40}{2} \times 9 \\ = 3600 J \\ W_{g} = 10 \times 20 \times 9 = 1800 J \\ \frac{W}{W_{g}} = \frac{3600}{1800} = 2 \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App