Question

I need help with the following.

Thanks!

An object is thrown straight upward How long will it take to reach its peak? Explain how you know. What will be its speed at the peak? Explain how you know. What will be its acceleration at the peak? Explain how you know. What will be its speed when it gets back to the same height from which it started? Explain how you know. How many m/s will it lose each second on its way up? How many m/s will it gain each second on its way down? Does air resistance increase or decrease the acceleration of a falling object? True or False: In the absence of air resistance, a heavier object will always land before a lighter object when dropped from rest at the same time.

Answer 1

​5)

• It will reach the highest point when the velocity in the vertical direction becomes zero. So, ​
  Substituting in
  $v=u+at$
  $0=20-10t$
  $\Rightarrow t=2sec$
• The velocity at peak point will be equals to 0, otherwise it will keep on moving.
• Acceleration at every point will be equal to g i.e 10 m/s2.
• Speed will be same as with which it was projected upwards i.e 20m/s due to conservation of energy.
• It will lose 10m/s per sec in way up
• It will gain 10m/s per sec in way down

6. Decreases

7. False, In absence of air resistance both heavier and lighter body will reach the ground at the same time as acceleration of the bodies will be same i.e g (acceleration due to gravity).

8. If surface area of the two bodies are different then different air resistance will act on the two bodies, so answer may differ.