PHYSICS HELP PLEASE #2!!!

[Anonymous32]

A student predicts that a steel ball dropped from rest from a height of 2 m will hit the floor
after 0.63 seconds. In their calculation they used an approximate value for the acceleration
due to gravity of g = 10 m/s2
.
The accepted value for the acceleration due to gravity is g = 9.8 m/s2
.
This means their calculated time will be:
A. unaffected
B. too long by about 1%
C. too short by about 1%
D. too long by about 0.2 seconds
E. too short by about 0.2 seconds

[exchemist]

56 minutes ago, Anonymous32 said:

A student predicts that a steel ball dropped from rest from a height of 2 m will hit the floor
after 0.63 seconds. In their calculation they used an approximate value for the acceleration
due to gravity of g = 10 m/s2
.
The accepted value for the acceleration due to gravity is g = 9.8 m/s2
.
This means their calculated time will be:
A. unaffected
B. too long by about 1%
C. too short by about 1%
D. too long by about 0.2 seconds
E. too short by about 0.2 seconds

This question clearly prompts you to do the calculation. You need the appropriate formula involving acceleration. What is it? 

[Anonymous32]

acceleration= change in velocity/time taken?

[Sensei]

1 hour ago, Anonymous32 said:

A student predicts that a steel ball dropped from rest from a height of 2 m will hit the floor
after 0.63 seconds. In their calculation they used an approximate value for the acceleration
due to gravity of g = 10 m/s2
.
The accepted value for the acceleration due to gravity is g = 9.8 m/s2
.
This means their calculated time will be:
A. unaffected
B. too long by about 1%
C. too short by about 1%
D. too long by about 0.2 seconds
E. too short by about 0.2 seconds

This is a clever question in physics.

Do you know the equation of the distance traveled by an object falling at a given acceleration? Reverse it to have time as result and distance and acceleration as parameters.

The distance is known. The acceleration is known. Only the time is unknown.

Have two such equations, but with different accelerations of 10 m/s^2 and 9.8 m/s^2, and divide them together and multiply by 100% to get the percentage difference, and subtract to have the absolute time difference in seconds.

[Anonymous32]

5 minutes ago, Sensei said:

This is a clever question in physics.

Do you know the equation of the distance traveled by an object falling at a given acceleration? Reverse it to have time as result and distance and acceleration as parameters.

The distance is known. The acceleration is known. Only the time is unknown.

Have two such equations, but with different accelerations of 10 m/s^2 and 9.8 m/s^2, and divide them together and multiply by 100% to get the percentage difference, and subtract to have the absolute time difference in seconds.

thank you so much, i was so stuck on it, this was very helpful!!

i also have two questions

1) when recording a force value, should it be to 2 significant figures

2)A car starts from rest and accelerates down a slope. The acceleration remains constant as the car travels from the top to the bottom of the slope. The average speed of the car is 2 m/s. The speed of the car as it reaches the bottom of the slope is: A. 0 m/s B. Between 0 m/s and 2 m/s C. 2 m/s D. Between 2 m/s and 4 m/s E. 4 m/s F. Greater than 4 m/s

[exchemist]

1 hour ago, Anonymous32 said:

acceleration= change in velocity/time taken?

No, that won't help you, because while you are told the acceleration you are not told the velocity. What do you know about this scenario? You know distance and acceleration and you want to calculate time. 

So the formula you need is the one that relates distance, acceleration and time. If you know two of them, and you do, you can find the third.

[swansont]

1 hour ago, Anonymous32 said:

1) when recording a force value, should it be to 2 significant figures

The number of significant digits depends on the precision of the data you have.

 

[Anonymous32]

thank you!