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3 years ago

When is the acceleration of a body is positive, negative and zero?

Physics

2 answers:

lyudmila [28]3 years ago

5 0

Answer:

In vector form , if angle between velocity vector and acceleration vector is less than 90° and greater than 0° then it is positive acceleration and if it is less than 180° and greater than 90° then it is negative acceleration. If there is no acceleration vector then it is called zero acceleration

Explanation:

defon3 years ago

3 0

Answer:

The acceleration is positive when it's in the same direction as that of velocity. It keeps on increasing the velocity. In this case, velocity is not constant.

The acceleration is negative when it is in the direction opposite to that of velocity. It keeps on decreasing the speed of body.

The acceleration is zero when the body moves with a constant velocity in any particular direction.

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An astronaut goes to Mars to do some experiments. Explain why her mass stays the same but her weight changes.

Snowcat [4.5K]

Because mass does not change from place to place but weight does change from place to place... why? because weight is the amount of gravitational force on an object and mass is the amount of matter in an object. mars has less gravitational force so an object will weigh less than it really weighs there

6 0

2 years ago

3. A pendulum with a 1.0-kg weight is set in motion from a position 0.04 m above the lowest point on the path of the weight.

gavmur [86]

Answer: K.E = 0.4 J

Explanation:

Given that:

M = 1.0 kg

h = 0.04 m

K.E = ?

According to conservative of energy

K.E = P.E

K.E = mgh

K.E = 1 × 9.81 × 0.04

K.E = 0.3924 Joule

The kinetic energy of the pendulum at the lowest point is 0.39 Joule

6 0

2 years ago

a skinny girl devours food that is equivalent to 600 kcal, as she is anorexic she repents and wants to lose twice as many calori

blondinia [14]

Answer:

Explanation:

Work done in lifting the weight once = mgh

= 20 x 9.8 x (1.9+1.7)

= 705.6 J

= 705.6 / 4.2 calorie

= 168 cals

Total energy to be spent = 600 x 10³ cals

No of times weight is required to be lifted

= 600 x 10³ / 168

= 3.57 x 10³ times

Total time to be taken = 2 x 3.57 x 10³

= 7.14 x 10³ s

=119 minutes .

4 0

2 years ago

Under ideal conditions (no atmospheric interference of any kind), if I hit a golf ball at an angle of 25 degrees at an initial s

g100num [7]

Answer:

The required angle is (90-25)° = 65°

Explanation:

The given motion is an example of projectile motion.

Let 'v' be the initial velocity and '∅' be the angle of projection.

Let 't' be the time taken for complete motion.

Let 'g' be the acceleration due to gravity

Taking components of velocity in horizontal(x) and vertical(y) direction.

$v_{x}$ = v cos(∅)

$v_{y}$ = v sin(∅)

We know that for a projectile motion,

t = $\frac{2vsin(∅)}{g}$

Since there is no force acting on the golf ball in horizonal direction.

Total distance(d) covered in horizontal direction is -

d = $v_{x}$ ×t = vcos(∅)× $\frac{2vsin(∅)}{g}$ = $\frac{v^{2}sin(2∅) }{g}$ .

If the golf ball has to travel the same distance 'd' for same initital velocity v = 23m/s , then the above equation should have 2 solutions of initial angle 'α' and 'β' such that -

α +β = 90° as-

d = $\frac{v^{2}sin(2α) }{g}$ = $\frac{v^{2}sin(2[90-β]) }{g}$ = $\frac{v^{2}sin(180-2β) }{g}$ = $\frac{v^{2}sin(2β) }{g}$ .