Name
Weight and Mass Date
In the physical sciences, mass (measured in kilograms, kg, or grams, g) and weight (measured in newtons, N) are different properties. Mass is a measure of the amount of matter in the body while weight is a measure of the force on the object caused by a gravitational field. Your mass then, would remain the same if you went to the moon, but your weight would change because there is less gravity on the moon’s surface.
On Earth, the acceleration due to gravity is
g = 10m/s2.
1. In the picture above, is the scale measuring mass or weight? Explain.
2. An object has a mass of 8.00 kg. What is the weight of the object on the earth? (Show your work.)
3. An object has a mass of 250 kg. What is the weight of the object on the moon? (Show your work, and use g = 2m/s2 for the moon)
4. The earth exerts a gravitational force of 500 N on an object. What is the mass of the object in kg? (Show your work.)
5. The earth exerts a gravitational force of 25 N on an object. What is the mass of the object in kg? (Show your work.)
When in equilibrium (at rest or at constant velocity), the total force or net force (Fnet) on an object is equal to zero. Fnet is the vector sum of all the forces on an object. For each of the problems below, identify the system and then carefully draw a force diagram for the system. Only after your have drawn the force diagram, use the standard problem solving format to determine the required quantities.
2kg
TBS
TBS
WBE
Find the tension in the each of the two strings supporting the ball. Fnet = 0 so TBS+ TBS = WBE
WBE = (2kg)(10N/kg) = 20N
TBS+ TBS = 2 TBS= 20N
so TBS= 10N
6. A grocery bag is capable of exerted an upward force of 45N before breaking. Can 5 kg of groceries be lifted at a constant velocity in this bag without ripping? Calculate the normal force the bag would have to exert on the groceries.
7. The plastic bag to the right holds 2.5 kg of food. What is the tension in each handle when it is held up at rest?
5kg
2.5 kg
8. The spider is hanging at rest from a thread that has a tension of 0.10 N. What is the mass of the spider?
9. The person and the sled have a weight of
1500 N. The dogs must exert a combined horizontal force of 300 N to pull the sled at constant velocity. Find the normal force and the force of friction on the sled.
300N
T=0.10N
1500N
10. A pendant hangs from chains that make a 90 degree angle to each other as shown in the diagram. If the tension on the left side is 4N and the tension on the right side is
3N, find the weight of the heart pendant.
4N
3N