PHYSICS MIDDLE SCHOOL

If a car changes its velocity from 32 km/hr to 54 km/hr, what is its acceleration?

Answers

Answer 1
Answer:

Acceleration = (change in speed) / (time for the change)


Change in speed = (speed at the end) - (speed at the beginning)


Change in speed = (54 km/hr) - (32 km/hr) = 22 km/hr


Acceleration = (22 km/hr) divided by (the time it takes to change the speed)

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A train is accelerating at a rate of 2 km/hr/s.  If its initial velocity is 20 km/hr, what is its velocity after 30 seconds?

Answers

Here it is. *WARNING* VERY LONG ANSWER

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11) If Galileo had dropped a 5.0 kg cannon ball to the ground from a height of 12 m, the change in PE of the cannon ball would have been product of mass(m),acceleration(g)and height(h) 

The change in PE =mgh=5*9.8*12=588 J 
______________________________________... 
12.) The 2000 Belmont Stakes winner, Commendable, ran the horse race at an average speed = v = 15.98 m/s. 

Commendable and jockey Pat Day had a combined mass =M= 550.0 kg, 

Their KE as they crossed the line=(1/2)Mv^2 

Their KE as they crossed the line=0.5*550*(15.98)^2 

Their KE as they crossed the line is 70224.11 J 

______________________________________... 
13)Brittany is changing the tire of her car on a steep hill of height =H= 20.0 m 

She trips and drops the spare tire of mass = m = 10.0 kg, 

The tire rolls down the hill with an intial speed = u = 2.00 m/s. 

The height of top of the next hill = h = 5.00 m 

Initial total mechanical energy =PE+KE=mgH+(1/2)mu^2 

Initial total mechanical energy =mgH+(1/2)mu^2 

Suppose the final speed at the top of second hill is v 

Final total mechanical energy =PE+KE=mgh+(1/2)mv^2 

As mechanical energy is conserved, 

Final total mechanical energy =Initial total mechanical energy 

mgh+(1/2)mv^2=mgH+(1/2)mu^2 

v = sq rt [u^2+2g(H-h)] 

v = sq rt [4+2*9.8(20-5)] 

v = sq rt 298 

v =17.2627 m/s 

The speed of the tire at the top of the next hill is 17.2627 m/s 
______________________________________... 
14.) A Mexican jumping bean jumps with the aid of a small worm that lives inside the bean. 

a.)The mass of bean = m = 2.0 g 

Height up to which the been jumps = h = 1.0 cm from hand 

Potential energy gained in reaching its highest point= mgh=1.96*10^-4 J or 1960 erg 

b.) The speed as the bean lands back in the palm of your hand =v=sq rt2gh =sqrt 0.196 =0.4427 m/s or 44.27 cm/s 
_____________________________ 
15.) A 500.-kg horse is standing at the top of a muddy hill on a rainy day. The hill is 100.0 m long with a vertical drop of 30.0 m. The pig slips and begins to slide down the hill. 

The pig's speed a the bottom of the hill = sq rt 2gh = sq rt 2*9.8*30 =sq rt 588 =24.249 m/s 
__________________________________ 
16.) While on the moon, the Apollo astronauts Neil Armstrong jumped up with an intitial speed 'u'of 1.51 m/s to a height 'h' of 0.700 m, 

The gravitational acceleration he experienced = u^2/2h = 2.2801 /(2*0.7) = 1.629 m/s^2 
______________________________________... 

EDIT 
1.) A train is accelerating at a rate = a = 2.0 km/hr/s. 

Acceleration 

Initial velocity = u = 20 km/hr, 

Velocity after 30 seconds = v = u + at 

Velocity after 30 seconds = v = 20 km/hr + 2 (km/hr/s)*30s = 

Velocity after 30 seconds = v = 20 km/hr + 60 km/hr = 80 km/ hr 

Velocity after 30 seconds = v = 80 km/hr=22.22 m/s 
_______________________________- 
2.) A runner achieves a velocity of 11.1 m/s 9 s after he begins. 

His acceleration = a =11.1/9=1.233 m/s^2 

Distance he covered = s = (1/2)at^2=49.95 m

NEED ANSWER ASAP!!! When a person goes jogging and then stops her kinetic energy is destroyed leaving her with less energy than she had before.True or False​

Answers

Answer:

Both True and False

Explanation:

This is because after she stops she may be able to store more energy than she had before but when she start off she may not. Hope this helps.

Answer: Answer is (false)

Explanation:

bother are correct but you will absolutely be marked as wrong if you put true

Because weight is a force, it is measured in ___________

Answers

Weight is a force.  This is a big part of the reason why weight
is described in terms of units of force. Some popular units of
force include newtons and pounds.
pounds because force is measured in pounds

Why didn't the first stars to form have solar systems with Earth like planets and satellites?

Answers

to be honest,no one probably knows.maybe because of their mass

Crying is a .........of distress to babies.

Answers

Crying is a signal of distress to babies.

Some reasons why babies cry: The baby is not feeling well, strange feeling that needs nappy change, a feeling of hot or cold, a feeling of tired and needs rest, a feeling of cuddling, feel like crying, and a feeling of hungry. 
Hey there

Crying is a signal of distress to babies.

Simple Machine Lever: A ________ that pivots on top of a fixed point called a _______.

Answers

A bar that pivots on top of a fixed point is called a lever.
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