You observe someone pulling a block of mass 48 kg across a low-friction surface. While they pull a distance of 3.0 m in the direction of motion, the speed of the block changes from 4.9 m/s to 7.7 m/s.
Calculate the magnitude of the force exerted by the person on the block.
This I figured out using moment principle and the position update formula. 282 N.
What was the change in internal energy (chemical plus thermal) of the person pulling the block?
How do I get this? I know that DEtot = q + W, I can find W and Kinetic energy. but what other energies would be included in Ei and Ef?
Please help soon!
To calculate the change in internal energy (DEtot), you need to consider the different forms of energy involved in this scenario.
1. Kinetic Energy (KE): This is the energy associated with the motion of an object. The initial kinetic energy (KEi) can be calculated using the formula KE = (1/2)mv^2, where m is the mass and v is the velocity. Similarly, the final kinetic energy (KEf) can be calculated using the final velocity.
2. Work (W): Work is the transfer of energy due to the application of a force over a distance. In this case, the force exerted by the person on the block causes the block to move a distance. The amount of work done (W) can be calculated as W = F * d, where F is the force and d is the distance.
3. Heat (q): Heat is the transfer of energy between objects or systems due to a temperature difference. In this scenario, it seems like there is no direct information about any heat transfer.
Now, using the change in total energy equation (DEtot = q + W), you can determine the change in internal energy.
Since there is no information given about heat transfer (q), we can assume that there is no change in thermal energy. Therefore, DEtot = W.
You have already calculated the magnitude of the force exerted by the person on the block to be 282 N by using the moment principle and the position update formula.
Now you can calculate the work done (W) by multiplying the force by the displacement (d): W = 282 N * 3.0 m = 846 J.
So, the change in internal energy (DEtot) would be 846 J.