4:chemical properties can only be observed when a substance changes into another substance.
5: physical properties such as color and shape are easy to observe
6: in a chemical change an altered substance forms
7: cooking or baking food will result in a chemical change
8: a melting ice cube is a physical change
9: the rusting of iron is a chemical change
10: water boiling is a scientific physical change
Explanation:
Given that,
A person walks 9.0 km directly east and then turns left and heads directly north for 12.0 km.
We need to find his displacement from the starting position.
We know that,
Displacement = shortest path covered

For direction,

Hence, this is the required solution.
Answer:
5 hours
Explanation:
formula is 6 km per hour
if you have to travel 30 km, divide 30 by 6
30/6 = 5 hours
Answer:
75 N
Explanation:
In this problem, the position of the crate at time t is given by

The velocity of the crate vs time is given by the derivative of the position, so it is:

Similarly, the acceleration of the crate vs time is given by the derivative of the velocity, so it is:
[m/s^2]
According to Newton's second law of motion, the force acting on the crate is equal to the product between mass and acceleration, so:

where
m = 5.00 kg is the mass of the crate
At t = 4.10 s, the acceleration of the crate is

And therefore, the force on the crate is:
