Physics -need help with forces?

Question

10. A person weighing 490 newtons is standing on a bathroom scale in an elevator that is acceleratinf upward at a rate of 0.2 meter per second squared. what does the bathroom scale indicate the person's weight is?
(a) 480 N
(b) 490 N
(c) 588 N
(d) 500 N
(e) 392 N

13. Two vectors, A and B, have componentgs ax = -2, ay = 3,
bx =1, and by=4. What is the magnitude of the vector A+B?

(a) 3.8
(b) 6.2
(c) 8.2
(d) 5.6
(e) 7.1

14. A 10 newton force is applied to two masses, 4 kilograms and 2 kilograms, respectively, in contact as shown below. the horizontal motion is along a frictionless plane. what is the magnitude of the contact force, P, between the two masses?
(a) 10 N
(b) 3.34 N
(c) 7.86 N
(d) 39.2 N
(e) 4N

Answer 1

10)

we know F = Ma, and we're trying to find the overall force. There are two different sources of acceleration in this case, one is gravity, the other is the elevator moving. So the total is just the sum of the two:
F = Ma1 + Ma2, a1 = gravity , a2 = elevator

The weight of the person (Ma1) is given as 490N, we can find their mass:
F = Ma1 = 490 = Mg, so M = 490/9.8 = 50kg

F = 490 + 50*a2, a2 is given as 0.2
F = 490 + 50*0.2
F = 490 + 10 = 500
answer is (D)

13) To find the magnitude of the sum of two vectors, you add the two vectors together and then use Pythagoras Theorem. Let's call the sum of the two vectors C, then we have:
A + B = C
Ax + Bx = Cx
Ay + By = Cy

So just plug in the numbers and you get:
Cx = -1
Cy = 7

Magnitude^2 = Cx^2 + Cy^2
= sqrt(1 + 49)
= 7.1
Answer is (E)

14) You'll have to explain the diagram? My guess is that the two objects are being pushed from the left, with 4kg on the left and 2kg to the right. If it's different, you'll have to sort it out yourself:

F = ma. The objects stay together, which means they accelerate at the same speed. The force needed to push both blocks adds up to the supplied 10N force:
F = ma
10 = (m1 + m2)a, m1 = 4kg, m2 = 2kg
10 = 6a
a = 1.6666

The blocks are accelerating at 1.6 m/s^2. Therefore, the force that is applied to the 2kg mass (contact force P) must be the force that is causing the 2kg mass to accelerate at that rate.

F = ma
F = 2*1.6666
F = 3.333

Answer is (B) (but only if the diagram you have matches what I explained above)

Answer 2

for number 10

490N + (490*.2) = 588

Remember there is already the 490N force with the additional force (.2m/s2 * 490) by the acceleration of the elevator.




for 13:

You need to add/subject the x and y components of the forces

ax (-2) +bx (1) = -1

ay (3) + by (4) = 7

The resultant force is -1x and 7y

To get the force vector you need the equation R^2 = X^2+y^2

R^2= -1^2+7^2=50

R= the square root of 50= 7.07 round up to 7.1


For 14:

What is the force acting on both blocks? 10N remember there is no fiction.

Answer 3

on an analogous time as your question is worded in a complicated way, i'm going to purpose terrific to describe. Gravity speeds up any mass down in the direction of the middle of the Earth. it somewhat is likewise represented as a rigidity, as F = mass*acceleration = mg An merchandise sitting on the floor won't flow down, besides the undeniable fact that gravity nonetheless acts upon it. for that reason, to counteract the rigidity of gravity (it extremely is needed for an equilibrium "static" situation wherein the chair isn't shifting), it somewhat is stated that there is an equivalent and opposite rigidity that pushes up on the chair to counteract the rigidity of gravity. This rigidity may be provided by potential of the floor the chair is sitting on. interior an analogous way, in case you have been sitting on the chair, you will possibly adventure the two a rigidity downward because of gravity, yet additionally a rigidity upward from the chair. for that reason, the two forces cancel out as they're in opposite guidelines, and additionally you do not flow up or down.