Answer:
2.5 kg
Explanation:
We can solve the problem by using Newton's second law:

where
F is the net force acting on the train
m is the mass of the train
a is the acceleration
For the toy train in the problem,
F = 3.0 N
a = 1.2 m/s^2
So we can solve the formula for m, to find the mass of the train:

Answer:
4) Isaac Newton was the first scientist to propose the idea that gravity increases distance between objects decrease
Explanation:
1 - Kepler may have inspired most of Newton's propositions, but there is no record of collaborating on the theory of universal gravitation.
2 - The universal gravitation theory resemble the works of other great scientists, but Newton was indeed the first to propose this idea of gravitation
3 - On the contrary, these scientists have shared concepts, with differences in accuracy that supersede each other to be accepted by the community (i.e: Einstein being at the forefront despite sharing some ideas with Newton)
Answer:
A) By applying a known force, and measuring it's acceleration.
Explanation:
This is actually something that astronauts do in space as a mathmatical exercise when calculating the mass of an object since F = m × a.
Once the force, and acceleration are applied, the only unknown is the mass which can be solved by dividing force over acceleration. This is because inertial mass is equal to gravitational mass.
Answer:
Not the right answer in the options, speed is 4.47 m/s, and the procedure is coherent with option A
Explanation:
Answer A uses mass and velocity units, which are momentum units. By using the conservation of momentum:
.
Since Tom stays in the raft, then both are moving with the same speed. From the options, the momentum is in agreement with option A, however, the question asks for speed.
Answer:
20000 pounds
Explanation:
Generally 1 gallon of fuel burnt gives of 20 pounds of CO₂
Difference in the gallons of fuel burnt

The 20 mpg car burns 1000 gallons of fuel more than the 30 mpg car
The amount of CO₂ would be

The fewer pounds that the 30 mpg car would release is 20000 pounds