1. e) None of the above is necessarily true.
2.d) Without knowing the mass of the boat and the sack, we cannot tell.
The constants could be the day because the experiment is all on the same day or the person throwing the pumpkin because it will always be the same perosn
Physical changes are those which do not affect the chemical properties of a substance. For example, when a paper is cut, the two pieces obtained are still paper. The chemical properties have not changed. Only, physically when one piece is cut to two. A chemical change occurs when the chemical properties change and a new substance with different chemical properties is obtained. For example, when the paper is burnt, it turns to ashes. Hence, this is a chemical change.
When a substance undergoes a physical change, the physical properties of the substance changes like the state (solid to liquid during melting), shape, size, volume etc. Many physical changes are reversible whereas, in general many chemical changes are irreversible.
The mass of the car is 2000 kg
Explanation:
We can solve this problem by using Newton's second law of motion, which states that the net force acting on an object is equal to the product between the mass of the object and its acceleration:

where
is the net force
m is the mass
a is the acceleration
In this problem, we have:
is the acceleration of the car
Each person applies a force of 400 N, and there are five men, so the total force applied is

Therefore, the mass of the car is:

Learn more about Newton's second law of motion:
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Answer:
Inelastic
Explanation:
The price elasticity of demand is the degree of responsiveness of demand for a product or service to a unit change in price. The demand for a product is said to be elastic when a change in price has a relatively large effect on the demand for the product, unitary when there is a percentage change in price brings about an equal percentage change in the demand for the product, and inelastic when a change in the price of a product brings about a smaller change in the demand for the product.
<em>In the case of the DVD rentals, a 10% increase in price brought about only a 5% drop in demand. Hence, the demand for DVD rentals is said to be inelastic because a change in the price brought about a smaller change in the demand for DVD rentals.</em>