# Newton's 1st, 2nd, & 3rd laws of motion

1. Jan 16, 2012

### xLuvux

a) A shirt left on your bedroom floor is still there after 2 days. (Newton's 1 law)

b) You run into your friend while ice-skating, & you both fall in opposite directions. (3rd law)

c) The horse you're riding trips on a tree stump & stops quickly, & you fly forward. (1st law)

d) A baseball continues rolling until it hits the fence. (1st law)

e) You hit a tennis ball w/ a tennis racket & the tennis ball sails over the net. (3rd law)

f) A person jumps off a diving board. (3rd law)

g) A swimmer swims through the water. (3rd law)

h) F=ma (Newton's 2nd law)

Can someone please check if I'm correct. Thank you.

2. Jan 17, 2012

### BruceW

they all look right to me.

3. Jan 17, 2012

### Andrew Mason

There is more than one correct answer here. Here is my take:

No net force: First law.
Net force down + collision: Second and third laws.
No net force (ignoring gravity): First law.
No net force (ignoring friction): First law.
Impulse imparted to ball by racket: I = Δp = FΔt; Second law.
Impulse imparted to diver by diving board: I = Δp = FΔt; Diver goes up and gravity brings diver down. Second law.
Swimmer's body pushes back on water moving water backward and swimmer forward; swimmer meets fluid resistance exactly equal to push of swimmer's body on water; 0 net force so swimmer moves at constant speed through water. First and third laws apply.
Second law if f≠0, but first law if f = 0;

AM

4. Jan 17, 2012

Thank you.