## 36 Unit 4 Practice and Assessment

#### Outcome 1

1) Which has greater between a kilogram of feathers and a kilogram of pennies? Which has greater ? Which has greater ?

2) What is the in of a 3 kg textbook?

3) (a) Convert your own weight from pounds to Newtons.

(b) Then calculate your mass in kilograms. Show all work.

4) The (g) on the moon is 1/6 that on the surface of Earth.

(a) Based on your answers to the previous question, what would your weight be on the moon?

(b) What would your mass be on the moon?

#### Outcome 2

5) For each object below, draw a :

a) A car hanging from a crane (there are two forces).

b) A car skidding to a stop (there are three forces).

c) A car with the parking brake set being pushed on by a someone, but not moving (there are four forces here, but two of them are the same type).

6) A person stands on a scale.

a) What type of force is pulling them down?

b) What type of force is provided by the scale to hold them up?

c) Draw a free body diagram of this situation.

7) A 7 N pushes on an object to the right and a 7 N force pushes on the object to the left.

(a) What is the ?

(b) Can the object be in ?

8) A 5 N force pushes on an object to the right and a 7 N force pushes on the object to the left.

(a) What is the net force?

(b) Can the object be in static equilibrium?

9) You push on a large box with 120 N of force, but it doesn’t move.

(a) How large is the force?

(b) Draw a of the situation.

#### Outcome 3

10)   You are helping a 48 lb toddler learn to float in a swimming pool.

(a) What weight of water must the toddler displace in order to float?

(b) What volume of water must the toddler displace in order to float?

(c) Currently the toddler doesn’t like water to cover his ears and holds his head mostly out of the water.  You notice that it feels as though he only weighs 3 lbs. Draw a free body diagram of the situationno post.

(d) How large is the on the toddler?

(e) If the toddler were to lower his head fully half-way into the water (past the ears), he would displace another 0.4 gallons worth of waterWould the toddler float then? [Hint: Water as a weight density of 8.34 lbs/gal]

11) An object has a of 0.5 m3 and weight of 150 N.

(a) What is the maximum volume of water it can displace?

(b) What weight of water can it displace?

(c)   Will it float?

(d) Is the object in the previous problem more or less dense than water?

#### Outcome 4

12) Calculate the density of the object referred to in the previous problem.

13) An object has a weight of 5.5 N and an of 3.5 N when fully submerged.

(a) Will the object float?

(b)  Calculate the of the object. 