Question

How much force is needed to stop a 120-kg ice-hockey player if he decelerates at 20 m/s²?

A. 20 N
B. 6 N
C. 240 N
D. 2400 N

@ksaimouli

Answer 1

It's either B. or D. .....

Answer 2

Hi Blossom...I think you can do this one!
Use Newton's 2nd law F=ma
see if you can do it...

Answer 3

It's D. 2400 N

Answer 4

as long as everything is in standard units, and it appears so, it is a simple multiplication problem at that point assuming you know the correct formula to apply :o)

Answer 5

But if it says the player decelerates at 20 m/s/s then shouldn't the force be negative??

Answer 6

Very good!

Answer 7

Yippee! XD

Answer 8

Thanks for your help! If I have more, can I tag you in them as well?

Answer 9

Something to remember...
Technically since the hockey player is "decelerating", it should be -20m/s not positive...but as far as the final answer goes, it doesn't make sense to have a negative force...thought I would add that in case you ever are curious :o)

Answer 10

You can tag me but I am doing differential equations right now and I haven't slept in awhile...I am just answering some physics to take a break...but if I'm available, I will try and help! :o)

Answer 11

Hm. Yeah, i think I understand. Thanks :) And if you are busy, then don't worry about it :)

Answer 12

:o)

Answer 13

is this your first physics class?

Answer 14

No... Well, this is my first year taking Physics, but I have been doing it the whole year...

Answer 15

Why?

Answer 16

(Also, I am on Unit 4)

Answer 17

I was just curious because Newton's laws were taught to me at the very beginning, I am just curious why they didn't teach them with your kinematics

Answer 18

O_O What are 'kinematics' ??

Answer 19

they didn't teach you kinematics yet?

Answer 20

Kinematics are questions like how far the ball goes if shot at an angle and initial velocity etc...didn't you have those yet?

Answer 21

Nope. I am only in eighth grade... So far I have learned: The Introduction to Physical Science (physical systems, measurement, and the international system), Matter (atoms, periodic table, and properties and states of matter) and Chemistry (bonding, reactions, formulas, mixtures, solutions, and substances) and now Force and Motion. :)

Answer 22

And nope, I don't think I have had those yet. Maybe it's the next unit?

Answer 23

Well since you are only in the 8th grade, that might explain it! :o)
Just keep in mind about what I said about a negative acceleration...those types of questions(whenever you get to them) will be asked like, "If a car is traveling at a constant velocity of 100m/s and begins "slowing down" etc..." The slowing down part is simply a negative acceleration :o)

Answer 24

Ah, okay! I will try to keep that in mind! :D

Answer 25

Anyhow, I posted the next question, any chance you could take a look at it?