Answer: D
Reduced impact time will increase the impact force
Explanation: Collision occurs when two or more bodies collide and exert forces on each other within a short time.
If a body of mass M moving with a velocity V collide with another body, the kinetic energy of the body is equal to the work done by the body.
That is, K.E = 1/2mv^2 = F × s
Where workdone = Force × distance
Make F the subject of formula
Mv^2/2s = F
But V = distance s/time t
Substitute for V
Ms^2/2t^2s = F
Ms/2t^2 = F
From the equation above, we can deduce that F is inversely proportional to the square of time.
Therefore, the reduced impact time will increase the impact force
Answer:
Force of static friction between the two surfaces
Explanation:
When two surfaces come into contact, they exert a force that resist the sliding of the two surfaces. This force is called static friction.
This force is given by the relation

Where,
μ - coefficient of static friction
η - normal force acting on the body
When a force acts on a body placed on a rough surface, it doesn't do any work if the applied force was less than the force of static friction.
So, in order to move the body, the applied force should be greater than the force of static friction.
Answer:

Explanation:
Given,
The angle of the slide=
The mass of the child is= m
coefficient of friction = 0.20
when she slides down now apply Newton's law


therefore the acceleration

![a=g[\sin \theta -\mu \cos \theta]](https://tex.z-dn.net/?f=a%3Dg%5B%5Csin%20%5Ctheta%20-%5Cmu%20%5Ccos%20%5Ctheta%5D)
![a=9.8\times [\sin 42^\circ -0.2\times \cos 42^\circ]](https://tex.z-dn.net/?f=a%3D9.8%5Ctimes%20%5B%5Csin%2042%5E%5Ccirc%20-0.2%5Ctimes%20%5Ccos%2042%5E%5Ccirc%5D)

hence, the magnitude of acceleration during her sliding is equal to 