1) A spring bathroom scale is designed to report the amount of upward force it's exerting on the objects touching its surface.(adsbygoogle = window.adsbygoogle || []).push({});

a) When you first step on the scale, you usually have some downward velocity because you "land" on the scale. As it slows your motion to bring you to rest, does teh scale report your correct weight, or does it report more than your weight or less than your weight.

*Greater than your weight.

b) If you stand motionless on one foot, rather than two feet, what fraction of your weight does the scale report?

*I belive it still reports your entire weight.

c) If you jump upward, what does the scake reoirt as you push yourself upward.

*Still your original weight?

d) You stand motionless on two identical scales, one foot on the left scale and one foot on the right. What can you say about the weights the two scales report.

*Their equal.

e) You stand motionless on two identical bathroom scales stacked ontop of each other. Each scale weights 10N. What weights do the scales report.(Bloomfield, 2001)

*The scale ontop of the scale reads your true weight and the one on the ground reads your weight + the one of the scale ontop of it.

2) Why would it be a bad idea to have your hand against the outfield wall while catching a batted ball? Explain (Beiser, 1992)

*It would be very painful because all of the force would be acting directly on your hand. There is no backward space to slow the ball down gradually.

3) The brakes of your car do work to slow the car down. If you slow from 20km/hr to 10km/hr, the brakes apply an average force over a certain distance. Assuming the brakes appy the same average force, how much further, as a friction of the first distance, will it take to slow the car from 100km/hr to 90km/hr? (Hint use the work energy principle and the definition of work)

*I don't have my book on me so I am just remembering this very rougly.

I know the work energy principle = W = (1/2mv^2) - (1/2mv2^2)

and work is defined to be the Force times distance of the cos of the angle.

I just don't know how to apply it to this problem since there is no mass.

4)At her highest point a 40kg girl on a swing is 2.0 m from the ground, while at her lowest point she is .08 m from the ground. What is her maximum speed? (Beiser, 1992)

*Help!

5)A 1000kg car strikes a tree at 30km/hr and comes to a stop in 15s. Find the intitial momentum and the average force on the car while it's being stopped ( Beiser, 1992)

*I think this problem requires the work enrgy principle as well.

Thanks for any help in advance.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# 5 quick hw problems

**Physics Forums | Science Articles, Homework Help, Discussion**